Head into "My Network Places"
On the left, click "view network connections"
You should have an icon called "Local area connection" with the 3com device name listed to the right of it.
Right click on it and select "properties"
Double click "Interent Protocol (TCP/IP)"
Select "Use the following IP address:"
For IP address, use "192.168.0.1
For subnet mask, use "255.255.255.0"
You can ignore the other boxes, go ahead and hit "OK"
Do the same thing on the other computer, except for "IP Address" use "192.168.0.2"
Let me know if this works without errors, cause then you are almost home free.