Laptops cannot read each other after installing AirCard

Laptop A-Compaq Presario (circa 2001) with Sierra 875 Aircard(Cingular. XP Home Edition OS. This is the Host.
Laptop B-HP Pavillion dv1000 (2006) XP Home Edition OS.
Computers connected by D-Link Gigabit Switch.
Both computers can easily share the internet but cannot “file share”. When the read each other “Access denied, you might not have appropiate rights….” error message displayed.

Is this a firewall related issue?
AP address issue?

When a router has been connected, since it is an aircard the router will not work…tech support for the router stated that is will not support an “aircard” connection????

Your help is appreciated!

Luis