I have a computer with a built in nic (Albatron kx600pro MB, 3com Nic) and it shares files terribly slow and lags out of every game we try over lan. After checking around I noticed that in the Lan connection service stats that "Packets Sent" keeps reseting back to 0 over and over. This is with a fresh install of winXp pro sp2 and I have tried removing the nic and reinstalling the drivers, reinstalling all lan protocols, and changing the cat5 cable to no avail. Its just this one computer, all others work fine connected to the switch. I cant figure it out please help.
Try setting your Network Card to 100/full duplex instead of Auto Negotiate. That will force it to work one way with the switch.
You might want to try connecting into a different port on the switch too.