Nah; Microsoft have 50,000 Employees. It depends at what point of the Lifecycle of a Windows Version you're talking about as to where programmers are. I'd imagine, with SP2 finished, and SP1 finished for Windows Server 2003 that around 20, maybe 30 of those - most of the actual Programmers at Microsoft - will be working on Longhorn at the moment.
Yeah; they have great Graduate Programs and Scholarship Programs. You'll end up going into IT not programming first off but you will have more than enough oppertunities to get into the Programming Groups.