Network?
15 minutes is too unbelievable if they're booting off a network image. Especially if everybody starts at the same time so you get several hundred machines hitting the server at once.
Even without a network boot, they're not going to be logged as "working" until the OS has fully booted and they've logged on to the appropriate "I am working" server. Which will probably slow to a crawl at shift changes.
Biting the hand that feeds IT
