If you try to access the folder and you get an Access denied, foo' prompt, then y0, it's time to take><0r teh NTFS pwnership. :evil:
To do that, you right-click the folder that you can't get into, choose the Security tab*, and then click the Advanced button, go to the Ownership tab in the new panel that appears, and give Ownership to the account you're using on the rescue computer.
* to get the Security tab on WinXP Pro, click Tools > Folder Options, go to the View tab, and at the bottom of the list, disable File Sharing For Simpletons. To get the Security tab on WinXP Home, you must boot the rescue computer in Safe Mode. There might be a command-line method, I haven't bothered to learn it if there is.
BTW no I haven't heard of this specific symptom as a virus thing, but there are over 170,000 known viruses/etc out there, so it probably is the case, specially if it's loaded with spyware and stuff.