Dilemma: Windows or DOS version of antivirus softwares

[forester]

There are two types of antivirus software, Windows and DOS version.
I was told that some virus locate themselves in the memory during the Windows startup, then most Windows-version antivirus softwares can't kill these virus, the only way to delete them is to boot the computer from floppy drive(or other removeable drive) where there is a DOS-version antivirus software, that is, only in the DOS environment, the virus can be cleaned up, not in the Windows.
I am not sure if this kind of remarks is correct, Thanks for any help!

[John E]

I'm 99% sure it isn't correct. First of all, modern versions of Windows are no longer running on top of DOS, so whoever advised you was probably just indicating that the virus gets installed prior to Windows appearing on screen. If a virus could only be removed at that stage, a decent antivirus package should be sensible enough to reboot the machine and remove it during the reboot.

The main problem occurs if a virus infects one of your system files. It used to be the case that viruses were separate programs that ran as a conventional process. However, more and more viruses are now written to infect system files such as mmsystem.dll and wmplayer.exe. These are much more difficult to remove because you need to keep copies of the uninfected files - but.....

That's what System Restore is for...! And that's what your antivirus package usually means when it says that it can't repair a virus - a system file has been infected and it can't remove system files because your computer won't work any more.

After removing a virus infection (i.e. one that actually got as far as infecting your machine) it's usually a good idea to use System Restore anyway, just to be on the safe side.

[JohnCz]

You have to use system restore very carefully. . . you may restore virus using system restore.

[mwilliamson]

Yeah, I've heard of virii infecting your restore directory too. WFP stops virii from infecting files needed to boot though, so usually the AV can remove anything. But if you are running an AV, it should catch it before it is even installed so no need to worry about this.