These are programs I use in my work to keep my Windows based computers clean of viruses and spyware. The best part is they are free. Of course you use these at your own risk - always be sure you back up your data before trying any of these programs.
AVG AntiVirus Free - Make sure you look for the free version as they have several commercial versions as well. I use this instead of Norton or McAffee, all of which I have had problems with being resource hogs.
Super Anti Spyware - Run this in the background when you boot up to protect from spyware.
Advanced Windows Care Personal - This is a great one-click maintenance solution that is easy enough to use on a daily basis. It checks for spyware, adware, registry problems, unneeded temp files, and startup programs.
Belarc Advisor - This program gives you a complete picture of your computer, along with information about installed programs and licence numbers. This is great diagnostic information to have printed out before you have problems.
The first thing you might want to try is to go to your Start>Accessories>System Restore to see if you can go back to a point before you got infected. If that doesn't work, and even if it does, run a complete virus scan with AVG. Also run Advanced Windows Care several times, rebooting in between runs.
Patience is the key here. Some of these scans take a long time to run and it's best not to sit there and watch it run. Start it and go do something else. Check it in a half hour and see how things are going.
If you still don't find anything, run a variety of scanning programs, such as these listed below. Running them several times is also a good idea, with reboots in between runs.
Ad Aware - Lavasoft's excellent product scans your computer for adware you may not know be running.
Spybot - Searches for spyware.
System Tools - Don't overlook the built in system tools provided in Windows for computer maintenance. These are to be found on the Programs>Accessories>System Tools> and are disk cleanup and disk defragmenter.
Best of Luck, and if you still have problems you can always contact me!