Try to check your hard disc for errors, you do it in this way ; Highlight your hard drive (normally it is C:), you find it in My Computer, right click on it and choose properties, select the second tab and choose "check this drive for errors", apply all the possibilities and press ok and restart the computer. Let the program run and then try again.

For be completely sure then you have to download the setup file again and reinstall it, you do it in this way : remove the software in Add and Remove programs in Control Panel, reboot the computer and install it again.

Then try to run Ccleaner,
Please see my article here on how do you use Ccleaner :

http://www.fixya.com/support/r3581476-how_to_use_ccleaner_to_keep_your_compute

Defragment you hard drive, you can use Defraggler here, that is better than windows own integrated :
http://www.piriform.com/defraggler
Portable (USB, no install) version you find here :
http://www.piriform.com/defraggler/download/portable

Now you have done all the possibilities, and your computer should be in good condition, but only one thing here, Your are Running onservice pack 2 !!??, you should update your machine at least to service pack 3, you find the updates in Internet explorer under the feature Tools (Windows Update), select it and follow the instructions on the screen, then choose quick search here and install the updates it find. You need to run it until Windows Update write "there is no more updates/ 0 updates".

One last thing, Is it windows xp 64 bit you are running or 32 bit ??, not all the programs are running under 64-bit version

Hope that helps
IF NOT then try to return here
Have a nice time over there