Have spent some days rescuing PCs that have not been maintained or protected against virus for months. One had over 1000 virus infected files and could barely start but I got it back to life.
Now today (Wednesday) I got a really tricky case. Whatever virus had hit this PC shut down every program you tried to start or run, including installing any antivirus software or running any software to change startup files etc. So what to do? Reinstall the whole thing and try to save documents etc?
I decided to try another tactic. I booted it using a Knoppix LiveCD, a special linux distrubition not meant to be installed but to diagnose or fix computers. After that I managed to install a linuxbased antivirus software and scan the computer and delete hundreds of infected files, still from the Knoppix LiveCD.
After that it started nicely with Windows, I could install an antivirus and get it up and running. A strange thing to use a free and open source software distro that Microsoft are doing their best to work against to save a PC using their proprietry and licensed operating system.