I usually use F-Prot for DOS - and it detects more than AVG Free Edition (yes, I have both).

For example, my copy of AVG Free Edition didn't detect the virus called "Klez" and variants.

I can only advise to use at least two scanners at the same time - what the one doesn't see, might be detected by the other one.

When you find a big kettle of crazy, it's best not to stir it.
--Dilbert cartoon

"Interplay.some zombiefied unlife thing going on there" - skavenhorde at RPGWatch