The maximum length of CAT 5 is around 120meters
I personally wouldn't push is past 100 metres.
When you plug the cable in to the PC and hub do you get any lights on the hub? If you do not then the cable is faulty.
Are you running IP? If so do a PING w.x.y.z where w.x.y.z is the IP address of another PC on your LAN
Is is wired as per the IEEE (I think that's the correct body) specs?
Have you considered using 802.11? It's a wireles protocol that can easily do 35 meteres - There are some security aspects to it but it works well.
HTH,
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Gary Williams