Don't worry, we'll find out what your router is What devices do you have that plug into your computer & into the cable outlet? Have a look at all the hardware you have (apart from comp & printer). Look for brand & model of anything extra. You must've logged into your router to try & enable UPnP... does it say a make & model when you bring up those router pages on your computer?

ISP is internet service provider... who do you pay for your internet access?
Is the XP firewall the only software firewall you have?