I'm sure that you have a router somewhere in your network, but it wasn't responsible for your current woes. Somebody either went astray while browsing or clicked when they should have closed.
Similar stories
and solutions are posted on
Geeks to Go! ,
Jet Insider and also on
Spybot Search and Destroy 's forum. BTW, Spybot Search and Destroy is a free and effective scrubber for this kind of junk. You can download it
here . Everyone who posted had experienced the same symptoms that you describe, so I think they are worth a quick read.
Going forward, make sure you have all Windows updates; there are 92+ (and counting) updates and patches needed after a clean installation of Windows XP Professional. You don't mention what antivirus software you're using. My recommendation is to pull them all out and give Eset's
NOD32 a try.