First try SFC (System File Checker).
It can fix certain issues in Windows where specific system files get corrupted, deleted, or infected. Basically the System File Protection watches the system files and checks their integrity against it's knowledge of what these files are supposed to look like. Generally if a system file get's "messed with" windows will let you know and give you the option to dissallow the change, sometimes you don't get this option though. The System File Checker is a command line utility that will initiate a scan of all the system files to make sure they are in their original state, present on the system, and or working properly. It's an easy tool to use but the user HAS to have an XP disk for it to work.
Do you have a valid XP cd?
If so, place it in your CD ROM drive and follow the instructions belowStart > Run > cmd
then typesfc /scannow (note the space)
let this run untill you get a message saying it is complete.SFC
- system file checker, retrieves the correct version of the file from %Systemroot%\System32\Dllcache or the Windows installation source files, and then replaces the incorrect file.
If you want to see what was replaced, right click My Computer > manage, expand event viewer > system.
Secondly, what antivirus and antispyware do you run? Are they updated and have you done full scans recently? We'll need to rule out infection.
If your scans find anything, please go to the malware
forum and follow the instructions at the top....Especially the CLICK HERE.
That will give you several steps that will help you clean up 70 percent of all problems by yourself. If at the end of the process you are still having difficulty (and you may not be) then post a hijackthis log in THE MALWARE FORUM
forum.(Posting HiJack This logs in any other forum other than the malware forum is forbidden. If you post an HJT log in any other forum, it will be removed and it will take you longer to get help, so please make sure you only post HJT logs in the malware forum)
If you are still having problems after getting a clean bill of health from the malware expert, please return to this