For those who run Windows and want to make sure their computer is safe. I highly recommend checking out Secunia's free online scanning and Secunia PSI a free download.
This security company is providing free for home users the ability to make sure all their programs are up to date and patched.
This means less vulnerabiltiy to hackers, virus's, and mal-ware. This does not replace your anti-virus, but is something to use in addition.
The Secunia PSI has been recommended by ZDNet, PCWorld Magazine, and CNET Downloads.
See the Secunia website here.
I have used Secunia PSI for 6 months and think it is something that everyone should use to make sure their comptuer is safe. Novice or Master of the comptuer this program is helpful.