I had a spyware attack that got through my defences a couple of weeks ago - I think it installed itself though a popup. The first thing I noticed was that my computer rebooted for no reason and then I had a warning about spyware in my system tray which continually tried to get me to install "xp-antivirus" software. An obvious trap, but one which no doubt catches many people.
While researching the symptoms and looking for fixes I discovered that the spyware had played with my OS - disabling windows firewall and forcing my browser to redirect away from helpful sites on spyware/malware like bleeping computer and spybot. It also stopped AVG and Spybot from accessing their update servers.
I found a neat way around the problem of the redirections though - I used free anonimiser sites to access the help forums and to download fixes. Malwarebytes found and removed the installed spyware, allowing me to update my antivirus and spybot software. A second runthrough by these tools identified the source files and removed them from my system.
I hope this helps anyone with the same problem!
(A week later my motherboard failed and I had to rebuild my PC but I think thats unrelated and doesn't detract from my great triumph over the Internet Gremlins)