To get rid of trailing or leading spaces try this:

$a = $a.Trim()

Or in this case:

$server = $server.Trim()

Powershell Get-WmiObject : Invalid namespace

Try this:

$namespace = "root\CIMV2"

Get-WmiObject -class Win32_Service -computername $computer -namespace $namespace

Also; $servers=get-content "c:\servers.txt" <---- Make sure there are no leading or trailing spaces or tabs in...