network is not connecting

Clarifications

The Power Cable into the device at the other end.

Or maybe you could post back with some more information about both this individual Computer and the Network that you are attempting to add it to. Little Unimportant things like

What is it?

Was it ever connected to a Network Previously?

If so was it a Workgroup or Domain?

If it was a Workgroup was it the same Name as the one that you are now connecting it to?

Did you setup Static Addressing?

What OS is involved here?

What type of Lead did you plug in?

Was it a crossover or Straight Through Cable or maybe even a Coax Cable?

You know little things like that would allow us to offer some assistance. ;)