I have had two computers in today which were infected with the dreaded Conficker Worm. This was the first time I had seen it in the wild.
You can download a free Conficker (sometimes called Downadup) removal tool from Sunbelt Software, makers of the superb Vipre Anti Virus/Anti Spyware.
If you keep your computer up to date with Windows updates you should be safe. If you are already infected, Conficker will stop you accessing Windows update, and possibly other security sites. It may also stop you transfering files from CDs, DVDs or Flash drives to your computer.
If you find you are unable to access certain websites, including Windows updates, download and run the Conficker removal tool. If your computer won’t let you download the tool, take a flash drive you have not used in your computer (because otherwise you may infect any computer you plug it into), and go a friend’s house or wherever you can get internet access.
Download and save the SSClean.exe file, and take it back to your place. Run the SSClean program from the flash drive. If you are infected you will get a message saying you need to restart and scan again. Do so.
You should now be able to download and run any Windows updates. Then run a full virus scan with your normal anti-virus. Then run SSClean again.