Quote - The end user must EXECUTE a file themselves for this to spread (at least under any reasonably up to date WinXP system).

That doesn't seem to be the case here. I did not execute ANY file, or click on ANY link. My computer is like Fort Knox. I have the latest versions of Adware and Spybot. I scan at least once a day for spyware/adware, if not 2 or 3 times. I use Mozilla/Firefox Browser and I adblock everything I see. If I run across a site that I need to view in IE, I do, but then I scan for adware/spyware immediately afterward. I delete cookies and temp files at least daily. More often than not, twice daily. I have Windows XP and am always current with updates. I have a router that my laptop is always connected to. I have a bought software firewall too. I virus scan twice weekly with up-to-date signatures, without exception. More if I have cause to be suspicious. I defrag my computer twice weekly. I empty the recycle bin right after adding something to it. I do not open email file attachments included in any email that I'm not expecting. If I'm expecting something, I save to my hard drive so I can see the extension, and then I scan the file first. If it's suspicious, I delete it. Am I anal about computer upkeep and maintainance? Yes, very much so. It's why I've never ever had computer virus; that was until last night. I did not mean to imply that MSN Messenger was the culprit passing along the virus. Perhaps I should have stated "through the MSN Messenger network". However, if you have MSN Messenger you are vulnerable to getting these messages and the worm because you are using MSN Messenger. I stress again, I did not click any links, or open any suspicious files, yet I managed to somehow acquire this "spread through the MSN Messenger Network" worm...seemingly from someone in my contact list who had (or still has) it based on a message I got a few days ago ... and even after my system showed as clean after 3 complete virus scans. So it appears you do not have to click anything or even open anything to get this particular worm. I've deleted that one person from my contact list until he figures out where he's being infected from. He claims he deletes it and it keeps reappearing, so he must be passing it back and forth with someone else in his list, and I can do without that headache.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi