Ok, I have a home network consisting of in total 9 pcs and a few xboxs
and playstation plus an ip camera of which only some of them are always
turned on ... All connected via a router and switches.

The always on PCs are two Win 7 pcs almost identical (same Dell model
slightly different cpu, 2.8Gb & 3.0Gb and vid card, nVidia versus ATI)
and the third is an old pc running XP with nothing special in it. The
other pcs, xboxs, ps's and ip camera don't seem relevent to problem.

The problem is that one of the Win7 pcs seems to always have some
problem with the network. Speficially it stops allowing the XP pc to
connect to it. It does not seem to matter what pc is the master browser
although if it is the XP pc the stoppage seems to take longer to
develope. The XP pc can always see the "good" Win7 pc and for that
matter any and all other devices if they're turned on also. Incidently
the IP camera is on the same switch and is always visible to all the
pcs. AND from the problem Win7 pc there never apopears to be a problem
and all devices are seen properly.

If I boot the XP pc nothing is changed. If I boot the Win7 pc all's well
for a period of time before the XP pc can't connect to the Win7 pc again
.... all of a sudden and for no apparent reason yet all other pcs remain
unaffected by "whatever" including other XP pcs if turned on.

It's just the one Win7 pc has the problemn and I'm at a loss to figure
out what's causing it. The troublesome pc has basically no software
installed on it as it used almost solely for connection to stereo and tv
as a multi-media player, gets updates as they come etc. etc. Doesn't
appear to be anything "rouge" on it etc.

I'm thinking of killing the onboard network card and installing a stand
alone card to see if that fixes the issue but other ideas more than
welcome at this point.