PowerShell Repair?

Is there a way to repair (or uninstall and reinstall) PowerShell v4? I’m getting the error below when running get-command and would like to set PowerShell v4.0 back to its “factory defaults” so I can play with version 4 and in particular DSC. (.Net 4.5 Framework is installed.) Thanks.

PS Env:\> $psversiontable

Name Value
—- —–
PSVersion 4.0
WSManStackVersion 3.0
SerializationVersion 1.1.0.1
CLRVersion 4.0.30319.18444
BuildVersion 6.3.9600.16406
PSCompatibleVersions {1.0, 2.0, 3.0, 4.0}
PSRemotingProtocolVersion 2.2

PS Env:\> get-command
get-command : Object reference not set to an instance of an object.
At line:1 char:1
+ get-command
+ ~~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:) [Get-Command], NullReferenceException
+ FullyQualifiedErrorId : System.NullReferenceException,Microsoft.PowerShell.Commands.GetCommandCommand