We Been having these issue for About 1 year now,
We have a network of 5 vista machines, 3 xp machine, 7 voip phone and 1 network printer.
The internet of all 3 windows xp machine keeps on dropping once everyday, removing the ethernet cable and putting the cable back doesn't help it, restarting the system doesn't help it, refreshing the ip doesn't, restarting the router either,
the only way I found to give them internet again is to manually set the ip and dns configuration daily.
If somebody out there has experience these same issues,
I would really appreciate your help.