Hi Cobra,
Can you please explain a little bit about your set-up and how the computers are all connected please? i.e. are there only two computers in total, and neither of them can see each other in the homegroup (or is there an existing homegroup that these two can't reach). Are the systems all connected to the same router?
Also, are there any errors you get? The more info you can provide, the easier it is to help

.