Peer 2 Peer connection

When I try to connect 2 PCs in Peer 2 Peer mode, I get the following msg from Windows XP:

“You do not have persmission to access the
network”

The main one that is having the problem is Windows XP and trying to connect it with a XP as well. The main one has a A7V8X mobo with a onboard Gigabit Ethernet card, AMD processor.

We have checked the cable, drivers, reformatted, still the problem is there. The main computer has
a cable internet connection which is connected to the USB port.

Sometimes it works and sometimes it doesn’t.

Any help is appreciated (extremely)