Chiming in.... I would say run a live-cd as well. However, i think you could do a little bit of active espionage while your at it. Your NTFS partitions will be read only, so go ahead and snoop around your NTFS partition, hda1 most likely, and check for anything obviously weird. i.e. files that you can't see in windows. Go ahead and follow everyone elses advice after that, testing for the software possibility. Does your linksys log anything? any recurring themes in the logs? like time, port, source address? Did you check your windows Event Viewer for anything strange? Since you've tried all the obvious, now you've got to look at stupid ****.

I would say though, that due to the time involved, its probably not your average run of the mill dooshbag. I'd say this person has to be connected to either you or your friend. Most likely an ex-boyfriend or an ex-girlfriend. Someone has it out for you, and really only you. Although, it could always be some dooshbag who you don't know.

Another suggestion I have, is get yourself an old crap computer like a Pentium 1 or 2 in its original configuration and install an IPCop box instead of your linksys. You'll get much better logging function, plus it has an IDS built in so you could get some clues as to how he's doing what he's doing. Look for patterns. It's going to be in the patterns somewhere. Also have the authorities clone your hard disk image. It will preserve their evidence, and then you can reformat your drive and really piss the guy off. He'll have to ACTIVELY recover his position. At this point, if you installed the IPCop box, have an idea of what he did. I would also suggest keeping ethereal nabbing packets the whole time. Play with the guy. Dick with him. Make him want to **** you over and then he'll get stupid.

Although, before you start dickin with some unknown person on the web, consider the consequence of him living down the street and murdering you and your friend. Oh, and taking obscene pictures of you two having double necropheliac hanky panky after. Oh, and then selling those pictures to some fetish site somewhere.