How to find source of network problem

OK, I looked at the computer reference materials and on the hardware websites, but did not see anything that answers this:

I have an XP machine connected to the internet through a Linksys router and a cable modem. For the last week or so, every so often (from 5 to 30 minutes) I will suddenly be unable to load any webpage. All the lights on the router and the cable modem are on. When I reboot the modem and router (unplug both, replug modem, wait for lights, replug router), everything works fine until the next failure. Unplugging and replugging either alone does not solve the problem.

This process is a bit of a pain in the butt, and I’d like to fix it. I assume that the problem is either in the router or the modem. Is there any test I can do to see which one of them it is? I could of course buy a new router, set it up, see if it has the same problem, and if it does return the router and repeat the same with the modem. However, this is both time consuming and esthetically displeasing, and I am sure a more elegant solution exists.

Anyone?

Try plugging your computer directly into the cable modem (remove the router from the setup). If the problem repeats itself, the problem is most likely the cable modem, otherwise the router is the issue.