Possible virus problem, need help.

[PhilipRoland]

Hey, everyone. New to the forums, and I signed up so I can get some help with a problem.

First off, I am not much of a techie, so I don't know if I'll be able to describe the problem articulately enough, but I'll try. I noticed about half an hour ago on a forum I frequent that I was not able to scroll all the way down on threads that had more than one page. It would suddenly cut off in the middle of a post and I would be unable to scroll the entire way down. I thought it was just the particular message board, so I went to a different one and had the same result. Suddenly my screen kept filling up with multiple Internet Explorer screens (and I don't even use IE, I use Firefox). I shut the computer off and turned it back on. The IE screens haven't returned but I'm still unable to scroll down on the message board threads and I'll still occasionally receive pop-up ads from Firefox. I'm not sure if that's the extent of the damage so far or if I'm yet to discover more. I haven't been to any new websites lately or clicked any strange links, and I haven't opened any attachments so I don't know how it came to be like this.

I've tried restoring my system, but it says that it has detected corruption on file OS ( C: ), and that I need to check it for errors before continuing. I clicked the link it provided to fix it, but it says that it can't check the disc while it's in use, and to schedule it to check it the next time I start my system up. I clicked the schedule check button and restarted my notebook, but I didn't see any confirmation of a check, and I'm still getting the same error message when I try to restore it.

Can anyone help? I'm at my wits end here. This isn't my computer (I'm housesitting for a friend) so I don't know what to do and I don't know anyone who can help me.

Thanks in advance, hopefully.