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function Get-RandomFreeDrive {
        $drivesinuse = get-PSDrive
        $rnd = new-object "random"
        $drives = ([int][char]"Z")..([int][char]"A")|?{[string[]]($drivesinuse) -notcontains [char]$_}|%{[char]$_}
        return $drives[$rnd.next($drives.count)]
    }