Three PCs with Windows98 I call them A, B and C

A PC has 100Mb PCI network card (3Com Fast EtherLink XL 10/100 NIC 3C905B-TX)

C PC has 10Mb PCI network card

B PC has two cards 100Mb PCI 3Com and 10Mb ISA (National Semiconductor Infomover ne2000)

A and B are directly conected with twisted pair cable with exchanged pairs.
B and C are conected with coaxial cable.

All PCs have installed IPX/SPX and TCPIP protocols.

Between PC A and B conection works (transferring files)
Bitween B and C conection is ok too.

But between A and C there is no conection.
So what should I do to get network working across the tho network cards (PC B)?

I need working both IPX and TCP protocols.
Please help

Thanks