problem with two network cards in one PC

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

Why are you doing this? Is there a particular reason you don't use the same media type (UTP) and a single net card in each or is it solely to avoid a hub? Mixed media will not work, use either all UTP or all coax.

I friend sold me the two 100Mb 3Com cards for a good price I thing ($70 including 10 meters cable)

The coaxial cable wich is between two of PCs is very long 40-50 meters and it is very difficult to change it with utp (it is between to buildings from 6 floor to 1 floor).

So you say I should use same media type. Is it 100% sure that it cant work with different medias?

Could I use (byu) a 10/100Mb hub with UTP and BNC port. I know that the bnc is only for 10Mb but I want to keep the conection between two of PCs (A and B) fast.

Could I try changing the speed (frame type from adnvaced settings for network card) for 100Mb network cards to 10Mb?