Using a program to wipe your drive to all zeros (or zeros, then ones, then zeros again, repeating <n> times...) is mostly a tool for gov't and the highly security conscious to ensure a hard drive contains no sensitive data before disposing of it (as surplus or scrap). If you are just reformatting to use the drive again yourself then save some time and do a quick format, it will get rid of viruses and spyware just as effectively as any other format/wipe. (Just make sure you do the format from a cd rom install disc, so it gets everything on the drive)

I can't recommend any great anti-spyware/anti-virus since the only virus i ever caught was the one i deliberately ran to see what it would do. I make my wife use MS one-care because it came with 3 user licenses and I gave one to my Dad, and the other I run on my work laptop mostly just to monitor the other 2.