If one of your contacts pops up in MSN Messenger with the message:
<friend> says: Hey, isn’t this YOU?? :S http://email@example.com
Don't click it !!
It's a trojan, you'll think your downloading a picture, but if you try to view it, it will unpack it's payload.
If I'm too late here's how I got rid of it:
In Task Manager:
Stop the process wkssvc.exe (google for this don't just take my word for it)
Disable the startup entry for it in msconfig (Start -> Run -> type 'msconfig' without quotes and press enter)
Delete the file %SystemRoot%/System32/wkssvc.dll (You may need to reboot first, or use something like procexplorer to kill any handles too it as the file will probably be in use preventing you deleting it initially)
Your AV should pick this up if it's up to date, some people have reported their AV stopping this trojan. Mine didn't !!! Bah! Luckily I smelt a Rat straight away.