It's important that you run an AV (AntiVirus) product on your PC at all times. Regardless of whether it's your personal PC, business PC, desktop, laptop or even a server, the consequences of succumbing to the effects of a PC virus can be catastrophic.
Just think for a moment if you lost all the work you'd been working on today with your PC. Now take that shock factor and multiply it by 5 so you can imagine what its like to lose a weeks work. Now, monthly, the last 12 months???? This highlights the importance of taking regular backups of your data but in addition to that, why not try to PREVENT the virus in the first place rather than recover afterwards?
Think about it, imagine even if your data is backed up each night and safely stred away on tape, it'll still take a few hours if not days to rebuild your PC's and re-install all of your applications.

For those of yo who have AntiVirus software (thats routinely updated) installed, here is a selection of sites on the Internet where you can perform a web-based virus scan of your system.

This can be a great way of routinely running AV (AntiVirus) scans of your machine/s if you don't own any AV software, or alteranatively verifying whatyou've got IS working by choosing an alternate software supplier.