ARRRRGGGGHHHH! This is killing me.

My son (yeah, same son as before) got a virus. . . again. His HP runs WinXP Home, and he has Avast antivirus. The virus he got is the one that pops up the "Windows Security Center" warning, and tries to get you to buy something to remove the virus it pretends to find.

I disconnected from the Internet, and removed some of the files manually. I installed Malwarebytesfrom a thumb drive, but I get an error telling me that the file mbam.exe cannot be found. I useda different computer to install Malwarebytes onto my thumb drive, but when I try to navigate to mbam.exe, it's missing.

I installed SmitFraudFix from a thumbdrive, but it needs to run from Safe Mode. That's when I learned that Safe Mode won't work. Each attempt to boot to Safe Mode results in a Boot Error screen, and the computer will ONLY boot to Normal mode.

I ran SmitFraudFix from Normal mode, but of course it fixed mothing.

I cannot access MSConfig. It opens. . . after about 20 minutes, but won't respond to the mouse or the Tab key.

I cannot run Hijack This.

Boot time Avast scans find many infected files and remove them, but does not repair any of the things I mentioned here. And the next time I connect the computer to the Internet, it starts downloading stuff.

The Restore Mode is also disabled, so in a fit of desperation, I ran Recovery Mode and reinstalled Windows. But it fixed NOTHING!

Now, thanks for listening to me whine. Here's my question. . . . short of reformatting, setting fire to his computer, or buying a new one, is there hope for this thing?