It seems that my version of Windows 7 (SP1, with PowerShell 4) lacks the certutil command. I tried to look for a way to add it manually but failed.
Any ideas on how to do it?
UPDATE
Thanks to comments, I was able to locate the certutil.exe file in \System32\ but I can't execute any certutil command.
Here's a snapshot I have:

C:\Windows\System32\certutil.exe– DavidPostill Nov 13 '15 at 13:53