WCF,
To confirm that TCP/IP is installed and working on each PC, do the following:
ping 127.0.0.1
ping loopback
ping localhost
ping (machine name)
ping (own IP address)
If any or all of these fail, then IP is not set up or configured correctly on the PC and you may have to investigate one or both PC's network card & IP stack further.
If all the above are OK it may be that one card is trying to communicate at a different speed (10 / 100) to the other, or is configured to work at a different duplex setting (full / half). Settings should be the same on both PCs - note that autodetect doesn't always work with a crossover cable.
The optimum connection would be 100 Full Duplex if both cards support it.
SD