Powershell start-process als aktueller Benuter mit adminrechten

PS C:\...> $user = "$thisuser"  
$pass = ""  
$cred = New-Object PSCredential($user,(ConvertTo-SecureString -String $pass -AsPlainText -Force))
ConvertTo-SecureString : Das Argument kann nicht an den Parameter "String" gebunden werden, da es sich um eine leere Zeichenfolge handelt.  
In Zeile:3 Zeichen:71
+ $cred = New-Object PSCredential($user,(ConvertTo-SecureString -String $pass -AsP ...
+                                                                       ~~~~~
    + CategoryInfo          : InvalidData: (:) [ConvertTo-SecureString], ParameterBindingValidationException
    + FullyQualifiedErrorId : ParameterArgumentValidationErrorEmptyStringNotAllowed,Microsoft.PowerShell.Commands.ConvertToSecureStringCommand

Main : A token belonging to the specified username was not found. Username: 
TestComputerTestComputer$
In C:\test.ps1:1639 Zeichen:1
+ Main
+ ~~~~
    + CategoryInfo          : NotSpecified: (:) [Write-Error], WriteErrorExcep 
   tion
    + FullyQualifiedErrorId : Microsoft.PowerShell.Commands.WriteErrorExceptio 
   n,Main
 

$proc = gwmi win32_process -computer localhost -Filter "Name = 'explorer.exe'"  
        #Go through collection of processes
        ForEach ($p in $proc) {
            $temp = "" | Select Domain, User  
            $temp.user = ($p.GetOwner()).User
            $temp.domain = ($p.GetOwner()).Domain
            $global:report += $temp
          }