cannot play games because version already exist

What installation CD did you use to install Ubuntu?
What version?
Does it ask for a password when you start them?
Has it ever worked?

What happens if you do the following:-

Applications --> Accessories --> Terminal
And in the terminal type:-

sudo synaptic

You should get a password prompt, then synaptic package manager should start?

Thank you for replying.

I used the Version 6.06 LTS for PC (intel x86) to install Ubuntu

When I click software properties of add/remove application, nothing happens, not even a screen asking for a password.

However, Synaptic package manager is working fine.
When typing:
Applications --> Accessories --> Terminal
And in the terminal type:-
sudo synaptic

I get:
Launching a SCIM daemon with Socket FrontEnd...
Loading simple Config module ...
Creating backend ...
Loading socket FrontEnd module ...
Starting SCIM as daemon ...
GTK Panel of SCIM 1.4.4

and Synaptic package manager opens.

Ok, that's good. What if you use the same procedure but instead of synaptic you launch gnome-app-install (which is the Applications --> Add/Remove application) and/or software-properties (which is unsurprisingly is the System --> Administration --> Software Properties application)?

I get the following message:

~$ sudo gnome-app-install
Password:
Traceback (most recent call last):
  File "/usr/bin/gnome-app-install", line 20, in ?
    from AppInstall.AppInstall import AppInstall
  File "/usr/lib/python2.4/site-packages/AppInstall/AppInstall.py", line 62, in ?
    from SoftwareProperties.aptsources import SourcesList, is_mirror
ImportError: cannot import name SourcesList
miryang@Phoenix:~$ sudo gnome-app-install
Traceback (most recent call last):
  File "/usr/bin/gnome-app-install", line 20, in ?
    from AppInstall.AppInstall import AppInstall
  File "/usr/lib/python2.4/site-packages/AppInstall/AppInstall.py", line 62, in ?
    from SoftwareProperties.aptsources import SourcesList, is_mirror
ImportError: cannot import name SourcesList

sudo software-properties
Traceback (most recent call last):
  File "/usr/bin/software-properties", line 78, in ?
    app = SoftwareProperties.SoftwareProperties(data_dir, options, file)
AttributeError: 'module' object has no attribute 'SoftwareProperties'

What is the contents of /etc/apt/sources.list which you can open with the text editor in Applications --> Accessories.

There were two source.list. One modified on Monday, and the other one modified on Dec. 10, 2006.
The following source.list was listed as modified on Monday.

deb cdrom:[Ubuntu 6.06.1 _Dapper Drake_ - Release i386 (20060806.1)]/ dapper main restricted
deb http://ca.archive.ubuntu.com/ubuntu/ dapper main restricted
deb-src http://ca.archive.ubuntu.com/ubuntu/ dapper main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://ca.archive.ubuntu.com/ubuntu/ dapper-updates main restricted
deb-src http://ca.archive.ubuntu.com/ubuntu/ dapper-updates main restricted

## Uncomment the following two lines to add software from the 'universe'
## repository.
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## universe WILL NOT receive any review or updates from the Ubuntu security
## team.
# deb http://ca.archive.ubuntu.com/ubuntu/ dapper universe
# deb-src http://ca.archive.ubuntu.com/ubuntu/ dapper universe

## Uncomment the following two lines to add software from the 'backports'
## repository.
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
# deb http://ca.archive.ubuntu.com/ubuntu/ dapper-backports main restricted universe multiverse
# deb-src http://ca.archive.ubuntu.com/ubuntu/ dapper-backports main restricted universe multiverse

deb http://security.ubuntu.com/ubuntu dapper-security main restricted
deb-src http://security.ubuntu.com/ubuntu dapper-security main restricted
# deb http://security.ubuntu.com/ubuntu dapper-security universe
# deb-src http://security.ubuntu.com/ubuntu dapper-security universe

#AUTOMATIX REPOS START

deb http://wine.lowvoice.nl/apt dapper main

deb http://www.getautomatix.com/apt dapper main

deb http://archive.canonical.com/ubuntu dapper-commercial main

deb http://archive.ubuntu.com/ubuntu dapper-backports main restricted universe multiverse

deb http://archive.ubuntu.com/ubuntu dapper-updates universe multiverse

deb http://archive.ubuntu.com/ubuntu dapper-security main restricted universe multiverse

deb http://archive.ubuntu.com/ubuntu dapper universe multiverse
#AUTOMATIX REPOS END

This was modified on Dec. 10, 2006.

deb http://ca.archive.ubuntu.com/ubuntu/ dapper main restricted
deb-src http://ca.archive.ubuntu.com/ubuntu/ dapper main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://ca.archive.ubuntu.com/ubuntu/ dapper-updates main restricted
deb-src http://ca.archive.ubuntu.com/ubuntu/ dapper-updates main restricted

## Uncomment the following two lines to add software from the 'universe'
## repository.
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## universe WILL NOT receive any review or updates from the Ubuntu security
## team.
# deb http://ca.archive.ubuntu.com/ubuntu/ dapper universe
# deb-src http://ca.archive.ubuntu.com/ubuntu/ dapper universe

## Uncomment the following two lines to add software from the 'backports'
## repository.
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
# deb http://ca.archive.ubuntu.com/ubuntu/ dapper-backports main restricted universe multiverse
# deb-src http://ca.archive.ubuntu.com/ubuntu/ dapper-backports main restricted universe multiverse

deb http://security.ubuntu.com/ubuntu dapper-security main restricted
deb-src http://security.ubuntu.com/ubuntu dapper-security main restricted
# deb http://security.ubuntu.com/ubuntu dapper-security universe
# deb-src http://security.ubuntu.com/ubuntu dapper-security universe

I didn't know which one you needed, so I am pasting both.

Thank you. I really appreciate your attention..

Ok, open each of the ones you have (as you did previously) and save them in your home directory (as a backup).

Then edit /etc/apt/sources.list again and paste what you see at this URL:-

http://paste.ubuntu-nl.org/37735/plain/

Which is a cut down version of what you already have.

Then try synaptic, add/remove and software properties again from the command line as you did previously. What happens?

I tried saving the source.list after pasting what you provided, but I get the message saying that I do not have permission to do so.

My mistake. I saved the new source.list, and I got the following

$ sudo gnome-app-install
Traceback (most recent call last):
  File "/usr/bin/gnome-app-install", line 20, in ?
    from AppInstall.AppInstall import AppInstall
  File "/usr/lib/python2.4/site-packages/AppInstall/AppInstall.py", line 62, in ?
    from SoftwareProperties.aptsources import SourcesList, is_mirror
ImportError: cannot import name SourcesList

 sudo software-properties
Traceback (most recent call last):
  File "/usr/bin/software-properties", line 78, in ?
    app = SoftwareProperties.SoftwareProperties(data_dir, options, file)
AttributeError: 'module' object has no attribute 'SoftwareProperties'

Can you run the following commands to see if they work:-

(assuming you did manage to save sources.list okay in /etc/apt ?)

sudo apt-get update
sudo apt-get upgrade

They're working. I ran both commands, but I'm only pasting the update. do you need the upgrade too?
Thank you for helping me out here. It's my time using Ubuntu, so I'm still at the getting-to-used-to stage.

~$ sudo apt-get update
Password:
Get:1 http://ca.archive.ubuntu.com dapper Release.gpg [189B]
Get:2 http://ca.archive.ubuntu.com dapper-updates Release.gpg [191B]
Get:3 http://ca.archive.ubuntu.com dapper-backports Release.gpg [191B]
Get:4 http://ca.archive.ubuntu.com dapper-proposed Release.gpg [191B]
Get:5 http://www.getautomatix.com dapper Release.gpg [189B]
Get:6 http://security.ubuntu.com dapper-security Release.gpg [191B]
Hit http://ca.archive.ubuntu.com dapper Release
Hit http://ca.archive.ubuntu.com dapper-updates Release
Get:7 http://ca.archive.ubuntu.com dapper-backports Release [23.3kB]
Hit http://security.ubuntu.com dapper-security Release
Get:8 http://archive.canonical.com dapper-commercial Release.gpg [191B]
Hit http://www.getautomatix.com dapper Release
Hit http://archive.canonical.com dapper-commercial Release
Ign http://wine.lowvoice.nl dapper Release.gpg
Hit http://wine.lowvoice.nl dapper Release
Hit http://www.getautomatix.com dapper/main Packages
Hit http://security.ubuntu.com dapper-security/main Packages
Ign http://wine.lowvoice.nl dapper/main Packages
Hit http://archive.canonical.com dapper-commercial/main Packages
Hit http://security.ubuntu.com dapper-security/restricted Packages
Hit http://security.ubuntu.com dapper-security/main Sources
Hit http://wine.lowvoice.nl dapper/main Packages
Hit http://security.ubuntu.com dapper-security/restricted Sources
Get:9 http://ca.archive.ubuntu.com dapper-proposed Release [23.3kB]
Hit http://ca.archive.ubuntu.com dapper/main Packages
Hit http://ca.archive.ubuntu.com dapper/restricted Packages
Get:10 http://ca.archive.ubuntu.com dapper/universe Packages [2458kB]
Get:11 http://ca.archive.ubuntu.com dapper/multiverse Packages [95.2kB]
Hit http://ca.archive.ubuntu.com dapper/main Sources
Hit http://ca.archive.ubuntu.com dapper/restricted Sources
Get:12 http://ca.archive.ubuntu.com dapper/universe Sources [975kB]
Get:13 http://ca.archive.ubuntu.com dapper/multiverse Sources [46.6kB]
Hit http://ca.archive.ubuntu.com dapper-updates/main Packages
Hit http://ca.archive.ubuntu.com dapper-updates/restricted Packages
Get:14 http://ca.archive.ubuntu.com dapper-updates/universe Packages [21.3kB]
Get:15 http://ca.archive.ubuntu.com dapper-updates/multiverse Packages [964B]
Hit http://ca.archive.ubuntu.com dapper-updates/main Sources
Hit http://ca.archive.ubuntu.com dapper-updates/restricted Sources
Get:16 http://ca.archive.ubuntu.com dapper-updates/universe Sources [3530B]
Get:17 http://ca.archive.ubuntu.com dapper-updates/multiverse Sources [427B]
Get:18 http://ca.archive.ubuntu.com dapper-backports/main Packages [13.0kB]
Get:19 http://ca.archive.ubuntu.com dapper-backports/restricted Packages [14B]
Get:20 http://ca.archive.ubuntu.com dapper-backports/universe Packages [41.8kB]
Get:21 http://ca.archive.ubuntu.com dapper-backports/multiverse Packages [2508B]Get:22 http://ca.archive.ubuntu.com dapper-backports/main Sources [4308B]
Get:23 http://ca.archive.ubuntu.com dapper-backports/restricted Sources [14B]
Get:24 http://ca.archive.ubuntu.com dapper-backports/universe Sources [10.2kB]
Get:25 http://ca.archive.ubuntu.com dapper-backports/multiverse Sources [1782B]
Get:26 http://ca.archive.ubuntu.com dapper-proposed/main Packages [54.8kB]
Get:27 http://ca.archive.ubuntu.com dapper-proposed/restricted Packages [14B]
Get:28 http://ca.archive.ubuntu.com dapper-proposed/universe Packages [5181B]
Get:29 http://ca.archive.ubuntu.com dapper-proposed/multiverse Packages [14B]
Get:30 http://ca.archive.ubuntu.com dapper-proposed/main Sources [17.4kB]
Get:31 http://ca.archive.ubuntu.com dapper-proposed/restricted Sources [14B]
Get:32 http://ca.archive.ubuntu.com dapper-proposed/universe Sources [1097B]
Get:33 http://ca.archive.ubuntu.com dapper-proposed/multiverse Sources [14B]
Fetched 3800kB in 1m46s (35.5kB/s)
Reading package lists... Done

Thanks Ben Goodger, that solved my question.