PS> 'C:\Program Files\Windows NT\Accessories\wordpad.exe'
C:\Program Files\Windows NT\Accessories\wordpad.exe
That didn't work because are far as PowerShell is concerned we gave it a string, so it just echoes it back to the screen. It did this because it parsed this line in expression mode. We need to tell PowerShell to parse the line in command mode. To do that we use the call operator '&' like so:
PS> & 'C:\Program Files\Windows NT\Accessories\wordpad.exe'
What's going on with this example is that PowerShell looks at the first non-whitespace character of a line to determine which mode to start parsing in. If it sees [_aA-zZ] or & or . or \ then PowerShell parses in Command mode. One exception to these rules happens when the line starts with a name that corresponds to a PowerShell language keyword like "if", "do", "while", etc. In this case, PowerShell uses expression parsing mode and expects you to provide the rest of the syntax associated with that keyword.