Problem Accessing Windows Pc From Mac


I have successfully mapped a network drive on a PC running Windows 2000 to a Mac running Tiger. Accessing files on the Mac from the PC isn't a problem but I'm having trouble doing it the other way! I have managed to 'Connect to Server', using the server address: smb://ipaddress, then I have picked the shared drive from the drop down menu and I have browsed the drive but after a few seconds I get disconnected. The network drive still shows in the finder but if I click it, it says the volume can't be found! I've tried to disconnect/eject but the icon stays there. If I try to connect again, it says that I'm already connected to the server volume. Any help on this would be greatly appreciated.
In System Preferences, select Sharing. Once in there, enable Windows Sharing. You should see a little message on how to access the Mac from the Windows machine. Follow the directions on the PC and it should be able to see the Mac.
Thank you but that isn't my problem. PC to Mac is fine. My problem is that when I go from Mac to PC, the network wont stay open. I can access the files for between about 45 secs & 2 mins then they disappear.