Odd freezing

Hey all.

So bear with me on this one, because I'm trying to troubleshoot my parents PC without actually being in the state that they're in. I've tried to get as much information on the problem from them but I'm not expecting a miracle, but hopefully it's something obvious to you all.

The computer is a Dell Dimension E310 hooked up to a Linksys G broadband router (Model # Wrt54G2 V1), which seems have caused the problem. The computer was originally hooked directly to a B2X (internet over radiowaves) internet, and worked fine. However, once the router was hooked up to it the computer started encountering weird freezes.

As I understand, the computer will freeze at completely random points, so diagnosing a software issue has been impossible. Apparently it has frozen: watching YouTube files, opening PDFs, hovering the mouse over a PDF file, browsing the internet.

My parents called a 'specialist' to look at the computer. He ran virus and spyware checks and found nothing and then 'reformatted' the harddrive. Though I don't believe he actually reinstalled windows fresh, I think its more misunderstanding what he did on my parents side. Apparently he also checked for any installed Linksys software and found nothing. My parents recall (my sister setup the router) that she put in a Linksys disk but apparently there's nothing to unistall.

For a few days, my parents were using it and it worked fine. They did all the things that had caused crashes previously without issue. Then apparently today, it froze some more.

I can't figure out what the problem can't be. If there are no viruses or spyware, and no linksys software and they haven't made any changes other than plugging in a router, I can't figure out what might be causing the problem besides a coincidental hardware issue.

Oh, and the router works fine broadcasting wireless. In fact they've been using my dad's laptop on the wireless since the tower went up.

Anyways. If you have any suggestions or thoughts on the issue I'd really appreciate your feedback. Thanks!