Everyone wants to avoid a sick computer. We have had very good luck using these virus protection programs. If you have a good one to recommend, please let us know.
Keep in mind, whatever protection program you use, nothing is 100%. And remember only open mail from sources familiar to you.

AVG Virus Protection (free)
Trend Micro House Call (free)
Norton Anti-Virus

Microsoft Updates can also help. Please remember...Microsoft will never
send you an email telling you to download a patch. Chances are the only thing you will get by doing this is a sick computer.