Most likely troublespots are:
1. Bad connections. Check that you have a link light on
all your cable connections. PC side, switch side, hub
side, etc.
2. Improper network settings or bad card drivers. Make
sure you have exactly the right, updated W2K driver for
your network card. Uninstall and reinstall the network
card with that driver. Redo your TCPIP settings (Check
with network administrator if you don't know these).
3. Try replacing the network cable.
4. Connection speeds. If the domain server only takes
10mbs and your card is 10/100, then check that the link
speed on your network IP settings is Auto/Negotiate.
Good luck. These problems aren't usually too bad.