I am a computer idiot - please help me

I feel so dirty. W32/bad trans-B worm (or is it a virus?) is in my mail program. Yes, I scanned and that is the only file infected. I have no clue how to rid this demon from my computer. I am apparently sending out dozens of e-mails to people on my address book, and thankfully they are being rejected and returned because of virus detection. But WTF do I do now? I am not a stupid person, just incredibly unversed in the ways of the computer. HELP!

This comes from Symantec’s website (the makers of Norton Antivirus). Click here for the specific page I got this from.

Sheesh, what a friggin’ mess. Thanks for the help, Mole. I did follow your instructions, and I think I might have fixed it. But now everything is running real slow, moving from my home page to SDMB took forever. Does that sound like I am still infected somewhere? Or has it done permanent damage to my computer? At least it is not disconnecting every few minutes, as was the case yesterday before I de-bugged. I don’t know why anyone gets their jollies from doing this to others, actually I do know - because it makes us pissed off and helpless. Anyway, thanks again. I hope that no one else here at SDMB has to deal with this. Yuck.