Are you sure the problem is malware? People often jump to that conclusion when there’s something wrong with their PC, and in my experience that conclusion is more often wrong than right. There’s a lot of malicious code in this world, but there’s even more code that’s merely incompetent. There’s also a fair amount of worn-out hardware.
On the other hand, if you’re experiencing any of the following symptoms, you quite likely have malware:
Your security software doesn’t work properly, or refuses to update.
Common programs for configuring and repairing Windows, such as MSCONFIG and System Restore, don’t work.
Messages from a program you never installed pop up and tell you that your computer is infected, your hard drive is dying, or you have some other serious problem. (See Watch Out for Rogues for more on this issue.)
Your browser’s home page keeps changing to something you don’t want, and/or your search results aren’t what they should be.
Your computer slows down sometimes for no apparent reason. (This may not be malware. See Very Slow PC for more on this.)
But what if you’ve got one or more of these symptoms, yet nothing in your battery of malware-fighting programs finds something evil?
The solution is to use a Linux-based malware-fighting program that boots off a flash drive or CD-ROM. By working outside of Windows, and outside the hard drive’s boot sector, these programs can better get around the malware’s defenses.
I’m going to recommend two of them, both of which can boot off flash drives or CDs. They’re AVG Rescue CD and Dr.Web LiveCD or LiveUSB. If one doesn’t do the trick, try the other.
My thanks to Coastie65 for introducing me to the Dr.Web programs in the original forum discussion.