BleepingComputer.com: Internet Connection Problem

I originally posted this in the Malware section but I was told my logs are all clean and that malware can't be causing my issues, so I was referred here. Hopefully someone here can help. When I first turn my PC on, I can't connect at all for about 15 minutes. Then I lose my connection every few seconds for the next 15 minutes. Once my PC has been on for about a half hour, my connection is absolutely fine until I shut down again. If I shut down and immediately restart, my connection is fine so it seems to have something to do with my PC being off for a while. There is no sign of any problem with my modem at all and my modem always shows that the connection is fine. And I never get disconnected after my PC has been on awhile. I checked my task manager right after I booted up to see if anything was running that shouldn't be, but I didn't see anything unusual. Any help in figuring this out is greatly appreciated. Thank you.

What version of Windows?

Connecting wireless? Wired?

Windows XP. Connecting through Westell Modem/Router 327W, wired.

Hey guys, was out of town for a while but I'm back now and just thought I would bump this to see if anyone else had any thoughts. Thanks.