One road you won't need to take to slenderise Windows Server 2008 is to run it as a 32-bit (x86) OS instead of 64-bit (x64). You've heard hype that the overhead of going to 64 bit, especially for virtual guests, is substantial enough to blow x64 off unless you know you need access to a 64-bit virtual address space (as if that knowledge were easy to come by). Dismiss this as noise. The 32-bit server OS is the HD DVD of IT, even for virtual guests. It's time to step into the future.
To put a fine point on the virtues of Windows Server 2008's trimmer physique, consider that I ran the x64 Windows Server 2008 Standard on an Apple MacBook Pro, running as a 64-bit virtual guest under VMware Fusion software virtualisation for OS X. Of MacBook Pro's 2GB of RAM, I reserved 512MB for Windows Server 2008. I made just one allowance for Windows Server 2008: I installed it on an off-board 18GB FireWire-powered hard drive. To be honest, that was for me. I wanted a blinky light that showed me how hard Windows Server 2008 was hitting the drive.
What-ux? Seen from one perspective, Microsoft wants to reach out to and play nice with Linux. Subsystem for Unix Applications (SUA) is bundled with Windows Server 2008 Standard, Enterprise, and Datacenter, and all Windows Server 2008 SKUs can compile and run many open source and commercial x86/x64 operating systems, OS X being a notable exception. Microsoft's decision, albeit one made under legal duress, to publish its proprietary APIs and protocols should make Linux developers and users of freeware Linux distributions ecstatic.