Have you tried including ‘> C:\MyFolder\Output.txt’ in the double quotes as well? Or even using Out-File to create the log? Something like this:
c:\windows\system32\WindowsPowerShell\v1.0\PowerShell.exe -Command “Get-childitem –Path c:\windows\temp –recurse –Force | measure-object –property Length –Sum | select-object Count, Sum | Out-File C:\MyFolder\Output.txt”
If I had to guess Powershell is putting out the results in its ‘session’ but it isn’t being returned back to the command prompt ‘session’ since you’re running the redirection outside of the shell. Hopefully that makes sense.