Hi if you have your xp cd then do the following you will not loswe any data execpt ie updates.Let menowhow things go after this also ccleaner is a good prgram but i dont think it will solve your particular issue.
•Insert your Windows XP CD into your computer's CD or DVD drive and reboot the computer. You should be prompted as to whether you wish to boot from the CD; press a key to allow the computer to boot using the Windows XP CD instead of the standard boot file. If you are not prompted to boot from the CD, restart the computer again and press "F12" on the BIOS page to access the boot options menu. From this menu, select the drive that contains your XP installation CD and press "Enter."
Wait for the "Welcome to Setup" page to appear. You will be given three options: setting up XP, launching the Recovery Console and quitting the setup process. Press "Enter" to enter Windows XP setup, even though you may be tempted to launch the Recovery Console instead.
Press the "F8" key when you reach the licensing agreement page to accept the agreement that is presented to you. Since you already have Windows XP installed on your computer, you will have accepted the agreement previously; it must be accepted again to proceed with your repair, however. If you do not accept the agreement, the setup program will exit and your existing installation won't be repaired.
Select your existing Windows XP installation from the list that is presented to you. Once it is selected, press the "R" key to begin repairing it. Make sure that you don't choose to install a new copy over it, since any saved data that you might have on the drive with your current installation could be lost.
Follow the on-screen prompts to continue through the repair process. The setup program will overwrite the damaged Windows XP files of your current installation without affecting any other data that you might have saved to your drive.
Wait while your computer reboots after the repair has been finished. Either remove the installation CD from your CD or DVD drive or simply don't press a key when asked whether you wish to boot from the CD, so that your copy of Windows XP will boot normally. Your repaired copy of XP should now boot without problems.
Read more: How to Repair an Existing Windows XP Installation | eHow.com http://www.ehow.com/how_5130638_repair-exi...l#ixzz0zY2kaJhF