If it continually comes back than I would tend to think it is a good detection and there is something restoring it. Also a google search for windvNT.sys returns no hits, which in itself is suspicious.
Have you tried the two on-line multi engine scanners in my post (re read the instruction in the previous post) ?
If you haven't already got this software, download, install, update and run it, preferably in safe mode,
Ewido anti-spyware. This should hopefully find whatever is restoring it also.
Do you have a firewall (hopefully not just XP's firewall ?
Any malware that manages to get past your defences will have free reign to connect to the internet to either download more of the same, pass your personal data (user names, passwords, keylogger retrieved data, etc.) or open a backdoor to your computer, so outbound protection is essential.
Also, whilst browsing or collecting email, etc. if you get infected then the malware by default inherits the same permissions that you have for your user account. So if the user account has administrator rights, the malware has administrator rights and can reap havoc. With limited rights the malware can't put files in the
system folders, create registry entries, etc. This greatly reduces the potential harm that can be done by an undetected or first day virus, etc.
Check out the link to DropMyRights (in my signature below) - Browsing the Web and Reading E-mail Safely as an Administrator. This obviously applies to those NT based OSes that have administrator settings, winNT, win2k, winXP.