Here’s a quick tip for tonight.
Microsoft has quietly developed a tool for use in situations where a computer just won’t start due to the number and/or severity of infections riddling it. Microsoft Standalone System Sweeper (MSSS) is not a replacement for a traditional antivirus which is designed continuously in the background checking for nasty stuff whilst MSSS is used after an infection has occurred.
In a nutshell, you download and burn the software to a CD or DVD or install it to a USB drive after which you boot directly from the media. Ideally, you should be creating the media on an uninfected machine to make absolutely sure the disc itself won’t be infected. The software comes in two versions (32-bit and 64-bit) so you will need to download the one that corresponds with the version of Windows on the infected computer.
If you’re one of those people that gets called upon to fix problems like malware infections you might be better off downloading and creating media for both the 32-bit and 64-bit versions and stashing it in your toolkit for future use. It’s also worth nothing that MSSS will only work on infected computers with Windows XP, Vista or 7 installed.
At the end of the day, this tool might help you recover a computer from the brink of a format and reinstall but I would still be rather suspect of the ongoing integrity of a Windows installation that had been compromised to the extent that it could no longer boot. I would use the opportunity to copy all the important data off the computer and then perform a clean installation as it is the only guarantee that the computer will no longer be infected.
If you want to download a copy of Microsoft Standalone System Sweeper you can get it here.