reykjavik,
If your ISP intends to make you pay for it, I'm pretty certain that you can complain to the Fair Trading people, as its not 'fair'. And even if you don't wanna go that far, just threatening to can often work....

An alternate option would be that if the ISP tries to make you pay, tell them you'll simply send a letter to the newspaper regarding it.. I think that whatever paper that ICON is in might be interested in this, as they just love to publish little articles that warn general users of an issue...

Also, I'd recommend you download The Cleaner, and run it to test and see if you do have a trojan on your computer as if it does, changing your password really aint going to do jack....