I'm having an odd problem with my Win 7 PC.

It randomly drops my internet connection down to so slow it's unusable. It doesn't appear to be totally off line, just super slow and unusable.
If I reboot, it connects properly.
This happens totally random, it may happen 3-4 times in a day, or not for several days.

My internet connection has been checked twice by my provider, so it looks like it's my PC.
My buddy is an electrical engineer in another city and he says it's a software problem.

I have no idea how to troubleshoot this, and I was wondering if I restored my PC to the original condition and reloaded everything if that might solve it.
Since I run a bare bones system with very little software and I keep all files backed up on DVD's, reloading and restoring everything isn't a big problem.
I'd just rather not have to do this unless it might fix the problem.

Any advice?????