I'll mark the Win9x VMs offline when there's nothing queued to run on them. Then in a weeks time I can delete them after all jobs referring to them have been retired/deleted (referential integrity in the database).
That means they even won't be available then for some specific corner-case tests (in which they are selected manually)? Hmm, is there much overhead involved to keep them "just in case"?
Regards,
Wolfram