Try upgrading your browser if is an upgradable version. (IE up to 6.0, Don't import your bookmarks et. al., save them separately and start fresh.)

And take whatever you know about the original msg & attachment, and search symantec.com for a cure. Cause you got yerself a virus there mate. If it was the more common persistent-porn-home-page problem, clearing the cookies would fix it.

Good luck. Now ya know--everything you receive from your friends was not necessarily sent by them.

W-O