Can't see other computers

Alright so I had windows 7 ultimate, I have had this problem TWICE now and I can't find anywhere that has my problem. So, when I go to network I can't see any of my family's computers except my dads work computers. I re-installed win7 because it happened to me the first time then I have had this new win7 for about a month and it happened to me again. I don't get it, I think it might be either a program or some kind of program blocking that port or something. I did a system restore and that didn't help. I have have a system image that I will try to use but I really don't because I installed quite a few things but, if I have to I will. So I would appreciate t if someone could help. I have my Specs updated if you need them.

EDIT: It got fixed I just turned network discovery on and off but I still might restore it with the system image cause my computer is a little messed up. But I still would like know what causes this? Next time I might not get so lucky and I hope to fix it without being confused by it. So any ideas?