Getting error

Please give us the output of this terminal commands...

lspci | grep -i vga

free -m

Then before to go deeply be sure your Ubuntu is fully updated/upgrade with no pending packages or install errors:

open a Terminal from the menu Applications->Accessories->Terminal

Tip: right click with mouse on the terminal title caption and select the item "Always on Top" doing this you will force the terminal window to stay on top of the other windows and you will find very easy to copy single row from this web page into the terminal...
Something more about using the terminal https://help.ubuntu.com/community/UsingTheTerminal

Then type or better copy and paste a row a time then press enter:
(Tip: select the single row to copy then right click into the terminal and to quick paste click with middle button of mouse )

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

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

Hope this helps

information you asked:

Q: lspci | grep -i vga

A: 00:02.0 VGA compatible controller: Intel Corporation 82845G/GL[Brookdale-G]/GE Chipset Integrated Graphics Device (rev 01)

Q: free -m

A: total used free shared buffers cached
Mem: 495 430 65 0 8 228
-/+ buffers/cache: 194 301
Swap: 1451 13 1437

sbproductions@sandbproductions:~$ sudo dpkg --configure -a
[sudo] password for sbproductions:
sbproductions@sandbproductions:~$ sudo apt-get -f install
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  linux-headers-2.6.32-23 linux-headers-2.6.32-23-generic
Use 'apt-get autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
sbproductions@sandbproductions:~$ sudo apt-get --fix-missing install
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
  linux-headers-2.6.32-23 linux-headers-2.6.32-23-generic
Use 'apt-get autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
sbproductions@sandbproductions:~$ sudo apt-get update
Hit http://archive.canonical.com lucid Release.gpg
Ign http://archive.canonical.com/ubuntu/ lucid/partner Translation-en_US
Hit http://archive.canonical.com lucid Release
Hit http://security.ubuntu.com lucid-security Release.gpg
Ign http://security.ubuntu.com/ubuntu/ lucid-security/main Translation-en_US
Ign http://security.ubuntu.com/ubuntu/ lucid-security/restricted Translation-en_US
Ign http://security.ubuntu.com/ubuntu/ lucid-security/universe Translation-en_US
Ign http://security.ubuntu.com/ubuntu/ lucid-security/multiverse Translation-en_US
Hit http://security.ubuntu.com lucid-security Release
Hit http://archive.canonical.com lucid/partner Packages
Hit http://security.ubuntu.com lucid-security/main Packages
Hit http://security.ubuntu.com lucid-security/restricted Packages
Hit http://security.ubuntu.com lucid-security/main Sources
Hit http://security.ubuntu.com lucid-security/restricted Sources
Hit http://security.ubuntu.com lucid-security/universe Packages
Hit http://security.ubuntu.com lucid-security/universe Sources
Hit http://security.ubuntu.com lucid-security/multiverse Packages
Hit http://security.ubuntu.com lucid-security/multiverse Sources
Hit http://pk.archive.ubuntu.com lucid Release.gpg
Ign http://pk.archive.ubuntu.com/ubuntu/ lucid/main Translation-en_US
Ign http://pk.archive.ubuntu.com/ubuntu/ lucid/restricted Translation-en_US
Ign http://pk.archive.ubuntu.com/ubuntu/ lucid/universe Translation-en_US
Ign http://pk.archive.ubuntu.com/ubuntu/ lucid/multiverse Translation-en_US
Hit http://pk.archive.ubuntu.com lucid-updates Release.gpg
Ign http://pk.archive.ubuntu.com/ubuntu/ lucid-updates/main Translation-en_US
Ign http://pk.archive.ubuntu.com/ubuntu/ lucid-updates/restricted Translation-en_US
Ign http://pk.archive.ubuntu.com/ubuntu/ lucid-updates/universe Translation-en_US
Ign http://pk.archive.ubuntu.com/ubuntu/ lucid-updates/multiverse Translation-en_US
Hit http://pk.archive.ubuntu.com lucid Release
Hit http://pk.archive.ubuntu.com lucid-updates Release
Hit http://pk.archive.ubuntu.com lucid/main Packages
Hit http://pk.archive.ubuntu.com lucid/restricted Packages
Hit http://pk.archive.ubuntu.com lucid/main Sources
Hit http://pk.archive.ubuntu.com lucid/restricted Sources
Hit http://pk.archive.ubuntu.com lucid/universe Packages
Hit http://pk.archive.ubuntu.com lucid/universe Sources
Hit http://pk.archive.ubuntu.com lucid/multiverse Packages
Hit http://pk.archive.ubuntu.com lucid/multiverse Sources
Hit http://pk.archive.ubuntu.com lucid-updates/main Packages
Hit http://pk.archive.ubuntu.com lucid-updates/restricted Packages
Hit http://pk.archive.ubuntu.com lucid-updates/main Sources
Hit http://pk.archive.ubuntu.com lucid-updates/restricted Sources
Hit http://pk.archive.ubuntu.com lucid-updates/universe Packages
Hit http://pk.archive.ubuntu.com lucid-updates/universe Sources
Hit http://pk.archive.ubuntu.com lucid-updates/multiverse Packages
Hit http://pk.archive.ubuntu.com lucid-updates/multiverse Sources
Reading package lists... Done
sbproductions@sandbproductions:~$ sudo apt-get dist-upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
sbproductions@sandbproductions:~$ sudo apt-get clean
sbproductions@sandbproductions:~$ sudo apt-get autoremove
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages will be REMOVED:
  linux-headers-2.6.32-23 linux-headers-2.6.32-23-generic
0 upgraded, 0 newly installed, 2 to remove and 0 not upgraded.
After this operation, 85.3MB disk space will be freed.
Do you want to continue [Y/n]? y
(Reading database ... 187796 files and directories currently installed.)
Removing linux-headers-2.6.32-23-generic ...
Removing linux-headers-2.6.32-23 ...
sbproductions@sandbproductions:~$ sudo apt-get update
Hit http://security.ubuntu.com lucid-security Release.gpg
Ign http://security.ubuntu.com/ubuntu/ lucid-security/main Translation-en_US
Hit http://pk.archive.ubuntu.com lucid Release.gpg
Ign http://pk.archive.ubuntu.com/ubuntu/ lucid/main Translation-en_US
Ign http://pk.archive.ubuntu.com/ubuntu/ lucid/restricted Translation-en_US
Ign http://security.ubuntu.com/ubuntu/ lucid-security/restricted Translation-en_US
Ign http://security.ubuntu.com/ubuntu/ lucid-security/universe Translation-en_US
Ign http://security.ubuntu.com/ubuntu/ lucid-security/multiverse Translation-en_US
Hit http://security.ubuntu.com lucid-security Release
Ign http://pk.archive.ubuntu.com/ubuntu/ lucid/universe Translation-en_US
Ign http://pk.archive.ubuntu.com/ubuntu/ lucid/multiverse Translation-en_US
Hit http://pk.archive.ubuntu.com lucid-updates Release.gpg
Ign http://pk.archive.ubuntu.com/ubuntu/ lucid-updates/main Translation-en_US
Ign http://pk.archive.ubuntu.com/ubuntu/ lucid-updates/restricted Translation-en_US
Ign http://pk.archive.ubuntu.com/ubuntu/ lucid-updates/universe Translation-en_US
Ign http://pk.archive.ubuntu.com/ubuntu/ lucid-updates/multiverse Translation-en_US
Hit http://pk.archive.ubuntu.com lucid Release
Hit http://pk.archive.ubuntu.com lucid-updates Release
Hit http://security.ubuntu.com lucid-security/main Packages
Hit http://pk.archive.ubuntu.com lucid/main Packages
Hit http://pk.archive.ubuntu.com lucid/restricted Packages
Hit http://pk.archive.ubuntu.com lucid/main Sources
Hit http://pk.archive.ubuntu.com lucid/restricted Sources
Hit http://pk.archive.ubuntu.com lucid/universe Packages
Hit http://pk.archive.ubuntu.com lucid/universe Sources
Hit http://pk.archive.ubuntu.com lucid/multiverse Packages
Hit http://pk.archive.ubuntu.com lucid/multiverse Sources
Hit http://pk.archive.ubuntu.com lucid-updates/main Packages
Hit http://pk.archive.ubuntu.com lucid-updates/restricted Packages
Hit http://pk.archive.ubuntu.com lucid-updates/main Sources
Hit http://pk.archive.ubuntu.com lucid-updates/restricted Sources
Hit http://pk.archive.ubuntu.com lucid-updates/universe Packages
Hit http://pk.archive.ubuntu.com lucid-updates/universe Sources
Hit http://pk.archive.ubuntu.com lucid-updates/multiverse Packages
Hit http://pk.archive.ubuntu.com lucid-updates/multiverse Sources
Hit http://security.ubuntu.com lucid-security/restricted Packages
Hit http://security.ubuntu.com lucid-security/main Sources
Hit http://security.ubuntu.com lucid-security/restricted Sources
Hit http://security.ubuntu.com lucid-security/universe Packages
Hit http://security.ubuntu.com lucid-security/universe Sources
Hit http://security.ubuntu.com lucid-security/multiverse Packages
Hit http://security.ubuntu.com lucid-security/multiverse Sources
Hit http://archive.canonical.com lucid Release.gpg
Ign http://archive.canonical.com/ubuntu/ lucid/partner Translation-en_US
Hit http://archive.canonical.com lucid Release
Hit http://archive.canonical.com lucid/partner Packages
Reading package lists... Done
sbproductions@sandbproductions:~$

your system is ok please give us the working kernel you are using still using terminal type:

uname -a

then please reboot your pc and hold the shift keyboard key at boot try to choose a different kernel number to try to see if it works without any issue.

if you still get freeze please don't press the power key to reboot...

Please note instead of press the Reset or power button to reboot the pc please try this:

To manage the freeze of your system and even Ctrl+Alt+Del doesn’t work anymore, the mouse is stuck on the screen any none of the key combinations will work, don’t think of the reset button just yet.

Hold down the Right Alt and SysRq keys and press this sequence:

R E I S U B

This will cleanly unmount drives, terminate processes and nicely reboot your machine.

http://en.wikipedia.org/wiki/Magic_SysRq_key

Hth

sbproductions@sandbproductions:~$ uname -a
Linux sandbproductions 2.6.32-24-generic #38-Ubuntu SMP Mon Jul 5 09:22:14 UTC 2010 i686 GNU/Linux
sbproductions@sandbproductions:~$
sbproductions@sandbproductions:~$

Im pressing Shift key but nothing is showing up.... ? and i m still having the same problem. Heeeeeelpppppp?

is this a just installed Ubuntu or an upgraded from prior release ubuntu...?
do you have the Ubuntu live cd...? if yes boot from that cd and please deeply check your ram memory using the menu item...
press shift when you see the lower man in the circle icon to have access to the requested menu item...

Please leave this mem test running for many hours... or stop it and change your RAM if you get red errors rows.

Hth

This a update of 9.4 and im upgraded to 10.4 LTS i don't have the live CD of 10.4LTS. I'll try the things you askd and will get back to you soon thanks

I hope you have upgrade from Ubuntu 9.10 to Ubuntu 10.04 or from Ubuntu 8.04 LTS to 10.04 LTS
http://en.wikipedia.org/wiki/List_of_Ubuntu_releases

upgrading from other release isn't supported...

yes i have upgraded from 9.10

Only a try, please remove compiz

Press Ctrl+Alt+F2 to get pseudo terminal then made login and the type this commands:
sudo apt-get remove compiz
sudo apt-get remove compiz-core
sudo dpkg-reconfigure -phigh xserver-xorg
sudo reboot

Hope this helps