Well my guess is that what Kent is trying to say is that for some reason KiXtart was unable to properly remove the drive mapping.

The portion that is missing in the UDF versions is what he posted already. Kent is not new here so I would assume he is already quite aware of all the Mapping UDFs.

SHELL '%COMSPEC% /C NET USE R: /D > nul'

Though, even NET USE has a persistent switch as well.