I very surprised when I install winxp x 64 and seen that my nic 3com 905TX not recognized.
May be anybody have drivers for this card?

You're surprised that a chipset released 10 years ago doesn't have x64 drivers?

But this very good chipset and it's one of the most commonly used.
In 3com site I didn't find drivers for my nic. I'm afraid that microsoft refuse to support this nic.

Microsoft doesn't make drivers. We include drivers for lots of common devices on the Windows CD, but only if the VENDOR supplies them.

1. The hardware vendor must supply drivers to Microsoft for inclusion on the Windows CD
2. The driver must meet WHQL certification to be put on the CD

Since 3Com doesn't make 64bit drivers for the hardware, Microsoft cannot provide them on the CD. Unfortunately for you, you'll need to buy a NIC with a newer chipset to get x64 support. I strongly recommend Intel 10/100(/1000) PCI NICs.