Determine installed PowerShell version

Question

How can I determine what version of PowerShell is installed on a computer, and indeed if it is installed at all?

Answer 1

To check if PowerShell is installed use:

HKLM\Software\Microsoft\PowerShell\1 Install ( = 1 )

To check if RC2 or RTM is installed use:

HKLM\Software\Microsoft\PowerShell\1 PID (=89393-100-0001260-00301) -- For RC2
HKLM\Software\Microsoft\PowerShell\1 PID (=89393-100-0001260-04309) -- For RTM

Source: this website.