I downloaded powerhsell from Microsoft website (http://support.microsoft.com/kb/968929) and installed it.
After successful installation I restarted computer and then open command prompt and write “Powershell” it shows me error “Add-PSSnapin : The Windows PowerShell snap-in ‘Pscx’ is not installed on this machine.”
To overcome that , download a 3rd party tool Powershell Community Extension from (http://pscx.codeplex.com/) and Install it. That will automatically override Profile.ps1 which was installed by powershell installation and will fix the problem.
Microsoft should add that in the installer.