The results only fetch me details from Windows Server Machines and Windows XP Machines. I do not get any output from my Windows 7 Machines although the WinRM Service is running on them. But strangely from over 100+ Windows 7 Machines in the network I get 2 Windows 7 Machines listed. All of the Windows 7 Machines except two fetch the RPC Server is unavailable error
What could be the starting point in trying to resolve this problem?
The RPC Server unavailable message is nothing to do with the WinRM service. Get-WmiObject uses DCOM to communicate with remote machines NOT WSMan (WinRM)
The message means that either the DCOM service isn't running on the Windows 7 machines or that a firewall is configured that is preventing WMI/DCOM access. Check that DCOM is available and that any local firewalls aren't causing the problem