If you are getting duplex mismatches you should be able to : (don't have Win2k box to test but in this case i think the flags are the same)

start -> run -> cmd
---> netstat -se

The 's' is for protocol statistics and the 'e' throws in ethernet. Look for Discards/Errors. Also note that you can add an integer to the end of it to have it run at an interval of that integer in seconds. This would be a useful thing to try while you are transferring to get an idea of whether or not you are receiving errors and at what layer...

Out of curiosity what protocol are you using for the transfer ?