Passing string variable as Argument in Powershell -

i'm trying write powershell script change drive letter of i: else. here's script.

$drivei = get-wmiobject -class win32_volume -filter "driveletter='i:'"  if ($drivei.serialnumber=""){      write-host "i: free..."  }   else  {      write-host "i: occupied"     foreach ( $s in @("'z:'", "'y:'", "'x:'", "'w:'", "'v:'", "'u:'", "'t:'", "'r:'", "'q:'", "'p:'", "'o:'", "'n:'", "'m:'", "'l:'", "'k:'", "'j:'", "'h:'", "'g:'", "'f:'", "'e:'", "'d:'", "'b:'", "'a:'"))     {         $testdrv = get-wmiobject -class win32_volume -filter "driveletter=$s"          if (!$testdrive.exist)         {             $s = '"'+$s.trim([char]0x0027)+'"'             set-wmiinstance -input $drivei -arguments @{driveletter=$s}             write-host i: has been moved $s             break         }     } } 

allow me walk through script. $drivei used retrieve information regarding i:. now, if i: has no serial number, indicates i: doesn't exist. if, on other hand, i: exists, i'm trying find drive letter free. i'm implementing search foreach loop. now, when call get-wmiobject, use drive letters single quote. when use set-wmiinstance, use double quotes. however, when modify $s wrapped double quote, doesn't work. in short, if use write-host $s, in output, say, "e:". when use set-wmiinstance -input $drivei -arguments @{driveletter="e:"}, works. when use set-wmiinstance -input $drivei -arguments @{driveletter=$s}, doesn't work. tell me i'm doing wrong?

don't put quotes in strings when you're going remove them later anyway. instead add quotes need them:

$driveletters = 'z:', 'y:', 'x:', ..., 'd:', 'b:', 'a:' foreach ( $s in $driveletters ) {     $testdrv = get-wmiobject -class win32_volume -filter "driveletter='$s'"      if (-not $testdrv) {         set-wmiinstance -input $drivei -arguments @{driveletter=$s}         write-host "i: has been moved $s"         break     } }