I've been wanting to jump into the Mac scene for awhile now, and these new iMacs are exactly the excuse I've been needing to force myself to do it. An iMac with a dual-core Intel chip? Man, two years ago that would have been unthinkable.
Try Trend Micro's house call to get a free, online virus scan. It's located here: http://www.trendmicro.com/hc_intro/default.asp Just do the anti-virus, you don't need the anti-spyware one that costs money to run.