OK this one should be fairly easy. I assume to boxes on the same hub.

1. Shut all firewalls
2. Check all leds, both on the hub as wel as the boxes nics. If one of them is out, check your cabling.
3. If thats all ok, open up a command prompt and enter "arp -a". This will display the current arp-cache of the box.
You should see the mac-adress of the other box. If no entries there we need to dig deeper.
4. Check your ip settings. If you use dhcp, they should've got ip settings from the dhcp-server. If static make sure they are both on the same subnet. For example use 10.10.10.1 255.255.255.0 and 10.10.10.2 255.255.255.0.
You can see these settings with "ipconfig /all" in a command prompt.
5. If this is all checked and adapted you should be able to ping from every box. If this works at least you have connectivity. Now this normally means applications will work too, but this is not always true. So you might need to enable netbios for example, if you wanna see shares between the boxes.

If this doesn't help reply, Cheers