Yes, it's possible to use Windows Server 2012 on your desktop. I used Server 2008 on my laptop a couple years ago and only a few things needed to be adjusted. One post above mentions an excellent website that I used to improve the experience.
Using it for my XBMC/Sickbeard setup Not really any modifications needed either, dunno if i could make anyone to optimize it further though, atleast it works fine currently.