[petgecko]

Best advice for protection from computer viruses:
DO NOT download attachments from -anywhere- that contain the extension ".exe"
95% of all computer viruses are spread by people that automatically click "ok" without paying attention to what they're agreeing to let their web browser or email program download to their computer. (these are called "Trojan viruses" after the Trojan horse, becuse they require action by the victim to get them to work)
As far as HTML or Plain Text email: A lot of legitimate companies use HTML-formatted email to show you photos of their products, and allow you "clickable" links to their web sites. Just make sure that you know where you're clicking to, and that the link is not a download link (your email program will ask you if you want to download, if it is.. don't let it!)
Best bet, do not open email from anyone that you do not know, and even if you do know them, it's still a good idea to type in any addresses, rather than just clicking the "click here" link.