Network Receive Is Horrendous

Ok, I have an old-school Pentium 233 Compaq machine. It runs great and I've never really had a problem with it, *but*, for some reason, the actual PCI/ISA bus architecture LOATHES receiving data. Trying three different NICs, alongside the same cable modem, the speeds are approximatley 2% faster than a 56k modem. Now, this is connected to a router which supports 10/100mbps and the other two computers, one a Pentium90 and the other a Celeron400 work brilliantly. The odd part is that if the user on the Celeron400 needs to transfer a file off of the Pentium233 onto the Celeron machine, it's like instant, at 100mbps. However, if it were the other way around, a 35k size file will take up to 10 minutes to transfer. I have no idea why it's like this, even after switching cables, network cards, etc. Any suggestions?