Microsoft Windows has expired

I'm on a friend's laptop whos managed to get a virus from an email attachment - document.txt.scr The virus scanner i've got can't find it, and google returns no results. It respawns windows when they are closed. Multiple windows appear with the following text: Microsoft Windows The license for this copy of the Microsoft Windows has expired. The software cannot be used until you obtain a new license. The fastest and most convenient way to obtain a license for your copy of Microsoft Windows is to fill the form below. To avoid data loss update your license as soon as possible.The licensing is free and your credit card will not be charged. Credit card number: Expiration date (mm/yy): PIN: IMPORTANT: Please provide us with your correct PIN number. any ideas?