Network much too slow

I've recently tried to copy some files - from an Athlon XP 2000+ to a Celeron 733 - with little success. The computer tells me it will take 45 minutes (!) to copy 80 megs. I could DOWNLOAD faster than that (which eliminates the possibility that the problem is on the Athlon, my computer). I'd like to know what's wrong. Atlhon has a 100mbit, full duplex card and the celly has a 10mbit, full duplex card. Only TCP/IP are on either.

What's wrong?

I had this problem once on a supposedly 10/100 PCMCIA network card...check the CPU usage on the Celery I'll bet its maxed out.

Fixed it, thanks for your answer anyway siyan, but I changed it to half-duplex and achieved transfer rates of 1.25mb/s (the rated 10mbits).