The Nyxem.E virus is due to hit in a couple of days. This one has been infecting computers through mass-mailing, and disables anti-virus software and will start destroying files (DOC/XLS/PPT/ZIP/RAR/PDF/MDB) on hard drives on 3 february (and, I think, every 3rd of the month thereafter).

F-Secure has a free disinfection tool called F-Force that will scan your computer for some of the worst of the worst viruses, including this one. I'd recommend downloading it and running it if you have a Windows machine (be sure to read the included instructions as you will need to download another zip file too).

Personally, I haven't been hit by a worm or virus or found any spyware on my machine in the last 15 years or so that I've been using Windows. I consider this partly due to luck and partly due to a high degree of familiarity with what my computer ought to be doing at any given time (being a programmer, I've learned to watch for anything unexpected because it might be one of my programs that's got a bug). Nevertheless, I don't consider myself immune and I'm running F-Force right now.

Remember, this virus is destructive. If you have it and the 3rd of the month rolls by, you will lose a lot of files you probably wanted to keep.