I caught a virus!!!
Or at least my PC did!
It showed up in an MSBlast.exe file, and thanks to McAfee virus scan online (yeah I'm plugging them okay!) it's now currently in quarantine while I figure out if it's safe to delete it or not.
Word from alt.computer says it's okay to delete but I may have to close down the 'system restore' option in order to delete it from there as well (not entirely sure how that works though and how long I'd need to shut that down)
Only realized there was something wrong last night when I got a nice little warning "your system will shut down in 60 seconds, please save all your work" etc.
anyway, fingers crossed it hasn't spread to anyone and apologies if it has.