Can't start PowerShell as administrator

I have Windows 7, and I want to run PowerShell as an administrator. I found it in the Start Menu, right clicked it and selected Run as administrator, but I get the following:

Windows Explorer has stopped working

Even if I I try to open PowerShell > Windows PowerShell Help, I have the same error. I only can start PowerShell as a regular user, but this is useless because I can't run the following command:

Set-ExecutionPolicy RemoteSigned
(ExecutionPolicy : Access to the registry key 'HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\PowerShell\1\ShellIds\Microsoft .PowerShell' is denied.)

Any ideas why I can't start PowerShell with admin rights?

you can run cmd.exe as admin and start powershell.exe