need help with a wierd network port-cant get conection with laptop

hello people, heres the problem.


i have one desktop pc conected to a network port (this port is conected to a router in some other office).

now here is the wierd thing, if i take the same cable and put it in my laptop, it wont connect to the network. (laptop works everyware else).
also i bought a network cable and it, wont work ither.
the only thing working is the one cable(the original cable) with the desktop pc and no other combination.

what is going on?

to make matters worse, i bought a hub, and throu the hub even the desktop wont conect, and also the leptop, but say, missing or damaged conectivity and both cant conect to the web.

what is going on?

thank you.