it's easy, do like this way
1. disable personal firware,
2. create user account in each PC,
3, make sure both working in the same Domain or workgroup.
4. check tcp/ip setting, make sure both working in the same subnet,
5, if still not working, manualy set ip address each pc, e.g.: on first PC, IP:192.168.1.1 subnet mask:255.255.255.0, and on the second PC: IP:192.168.1.2, subnet mask:255.255.255.0
this method always working, you can try it.