internet and network problems

Ive begun having problems with our network, I cant ever see anybody else anymore, our main computer can see me, but nothing whatsoever *on* me (even my Shared Documents folder), and our third computer can see me just fine

fortunately, though, I can still access the internet somehow, but recently, thats deteriorating too...I havent timed it, but I estimate it can be left on for about half a day or so, and it suddenly is no longer able to access the internet...it always happens while Im away, but I dont know if thats a good or bad thing (doesnt interrupt something I was doing, but its so unexplained!)...I suspect it somehow has something to do with the screensaver, and how it logs off when it kicks in, though Im not aware of any supporting reason at all, just a whim

I have Windows XP Home, and in the device manager window under network adapters, it says I have a Broadcom 440x 10/100 Integrated Controller...if any more information is needed, from either this one or our local gateway/main computer, ask and I can check

also, I have another profile on this computer that I use when I go over to a friend's for a LAN party, and have it set up where we dont have to get it reconfigured every time...I dont know if that would be important, as I dont see how settings on one profile would change settings on another, even though I do occasionally use the other one here at home (would it maybe be changing non-profile settings?)

thank you to anyone who can offer advice, even if its just a lead or idea