It sounds like the file that was infected may have been needed for Windows. Now Windows is unstable.
Try running CHKDSK /F.
Run Windows XP normally, allowing it to load fully.
Access the "My Computer" menu. You can do this by clicking the Start menu and clicking the "My Computer" menu option. You can also double-click the "My Computer" icon if you've enabled it on your desktop.
Right-click on the drive on which you wish to run the Chkdsk F command.
Click "Properties" in the right-click context menu.
Click on the "Tools" tab in the Properties window.
Click on the "Check Now" button in the "Error-checking" frame of the Tools tab.
Click in the "Automatically fix file system errors" check box under the "Check disk options" frame in the following window. This is the step which enables the "/f" command in Chkdsk.
Click "Start" to begin the Chkdsk scan. If there are a lot of processes running in the background, or if Chkdsk determines that it should be run when you next restart your computer, it will suggest it. It is always advisable to run the Chkdsk from the restart in this case.
Or, if your computer reboots during this process, you can do it manually.
Start your computer in safe mode by pressing F8 during the startup process before you see the Windows logo showing that windows is loading. From the menu, select Safe Mode with Command Prompt.
Once at the Command Prompt window, type "chkdsk /f" (without the quotes).
Edited by possumbarnes, 31 May 2009 - 02:21 PM.