Powershell script to install software.

I have created a powershell script to start the install of a software package, ".exe". I know the script is running because I have it writing to a log file, I can run the script outside the logon process and it will work just fine. To verify that it was not starting the exe I have it just starting notepad.exe. Below is a sample, neither will start notepad in the logon process but the add-content will write to the log file.

add-content \\app1\Logs\log.log"$now,$computer"
invoke-command "C:\windows\notepad.exe"
Start-Process "C:\windows\notepad.exe"

Ideas?