Vijayshinva Karnure of Microsoft India offers up some advice about using Windows Server 2008 as a desktop OS. To be perfectly honest, I don't recommend this, because you lose too much of what makes desktop versions of Windows special (i.e. things like Media Center) while introducing potential compatibility issues. Anyway, here's what he's got to say...
Windows Server 2008 is the best OS to be released [to] date from Microsoft's stable. And the moment I got hold of the RTM build I could not resist installing it on my workstation. Due to the nature of my work I always prefer running a Server OS on my main workstation... I have been running Windows 2003 disguised as XP (with all the themes and stuff) all these days.
So here is my tale of how I went about setting up Windows Server 2008 to look and fell like its desktop counterpart Windows Vista.
1. Enable Hardware Virtualization
2. Install the latest Graphics and Audio drivers
3. Desktop Experience Feature
6. Disable Shutdown Event Tracker
9. Get a codec pack.
10. Enable Hyper-V