whenever i click on the add/remove button on the applications, an error occurs. also, i cannot install softwares like python tkinter and limewire! please help . . .

Please copy and paste this into your /etc/apt/sources.list file

#deb file:///home/neo/Desktop/M54SS/cam/UVCDriver_Ap_Ubuntu7.10/luvcview-20070512 deb/
#deb http://us.archive.ubuntu.com/ubuntu/ gutsy main restricted
#
# #deb cdrom:[Ubuntu 7.10 _Gutsy Gibbon_ - Release i386 (20071016.1)]/ gutsy main restricted

# deb cdrom:[Ubuntu 7.10 _Gutsy Gibbon_ - Release i386 (20071016.1)]/ gutsy main restricted
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.

deb http://ph.archive.ubuntu.com/ubuntu/ gutsy main restricted
deb-src http://ph.archive.ubuntu.com/ubuntu/ gutsy main restricted

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

## 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://ph.archive.ubuntu.com/ubuntu/ gutsy universe
deb-src http://ph.archive.ubuntu.com/ubuntu/ gutsy universe
deb http://ph.archive.ubuntu.com/ubuntu/ gutsy-updates universe
deb-src http://ph.archive.ubuntu.com/ubuntu/ gutsy-updates universe

## 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
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb http://ph.archive.ubuntu.com/ubuntu/ gutsy multiverse
deb-src http://ph.archive.ubuntu.com/ubuntu/ gutsy multiverse
deb http://ph.archive.ubuntu.com/ubuntu/ gutsy-updates multiverse
deb-src http://ph.archive.ubuntu.com/ubuntu/ gutsy-updates multiverse

## 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://ph.archive.ubuntu.com/ubuntu/ gutsy-backports main restricted universe multiverse
# deb-src http://ph.archive.ubuntu.com/ubuntu/ gutsy-backports main restricted universe multiverse

## Uncomment the following two lines to add software from Canonical's
## 'partner' repository. This software is not part of Ubuntu, but is
## offered by Canonical and the respective vendors as a service to Ubuntu
## users.
# deb http://archive.canonical.com/ubuntu gutsy partner
# deb-src http://archive.canonical.com/ubuntu gutsy partner

deb http://security.ubuntu.com/ubuntu gutsy-security main restricted
deb-src http://security.ubuntu.com/ubuntu gutsy-security main restricted
deb http://security.ubuntu.com/ubuntu gutsy-security universe
deb-src http://security.ubuntu.com/ubuntu gutsy-security universe
deb http://security.ubuntu.com/ubuntu gutsy-security multiverse
deb-src http://security.ubuntu.com/ubuntu gutsy-security multiverse

The open a Terminal from the menu Applications->Accessories->Terminal and type:

sudo dpkg --configure -a
sudo apt-get -f install
sudo apt-get clean all
sudo apt-get update
sudo apt-get upgrade
sudo apt-get dist-upgrade
sudo apt-get clean all
sudo apt-get autoremove

then please reboot your system, type

sudo reboot

give your user password when requested, you don't see nothing when you type it, then press enter.

Hope this helps

sorry . . . i'm a bit confused . . . how should i paste the "things" that you made? should i open the terminal and type /etc/apt/sources.list file ?

thanks . . . my laptop is now working well . . . i no longer consider changing the OS to windows xp . . . hehehe