Home network help

I have 4 computers networked using 3Com HomeConnect phone line PCI cards:

Computer A has Win98 SE.
Computer B has WinXP.
Computers C & D have Win2k.

All of the computers can ping each other and consistently get replies. The problem is tryingto share files.

Computer A can see all of the computers and access their files, but none of the other computers can see Computer A. Computers B, C, & D can all see each other and share files just fine.

I’ve tried various network troubleshooters in Windows, and ones that I’ve found on the web. Nothing’s helped so far.

Any help is greatly appreciated!

Thanks in advance,
Phillip Harrison