Windows 7 not showing other computers on network

Just check your windows firewall.. disable it then check that network PC's are showing or not.

Other solution:- In windows 7 there is option for network to chose that it is "home", "work" or "public" network. Just go network from bottom right corner of your task-bar n/w icon and change the n/w to HOME or WORK n/w.. i think you problem will be solved.

At last if not solved then disable your antivirus firewall and check.