Yeah, you can basically set it so that when Windows opens, it'll open up XBMC in full screen straight away.
Have you researched XBMC at all? That thing is awesome!
You'll probably find it a chore renaming all of your video files, but once you do that, it'll pull all the movie information/video covers etc from IMDB, so it looks like a normal movie planner/Netflix I suppose. Takes a little time to get to grips with, but I'd definitely recommend it.
One problem I have encountered though was when I used WiFi to a networked drive, your computer would sometimes try to find the networked drive before it was connecting to the network, so I had to open up 'My Computer' and open the drive through that once connected before XBMC would recognise it.
With your fileserver, it sounds like it might be some time off yet, but it might be a good idea to start researching between unRaid and FlexRAID.
I've currently got unRaid on mine, it's a very basic OS that is designed for fileservers, I'd probably say it's the best OS/software out there that you can get for a fileserver. How, it's functionality is pretty limited for anything else. You can get certain 'apps', and I've managed to set up a Teamspeak server on mine. But that's about where it ends.
But, when I upgrade my PC, I'm going to have a i7 2700k spare, and I need a bigger case anyway for my server 'cause I've already hit the max 6 hard drives, so I'm installing Windows back on it, and then I plan to use something called FlexRAID, the last time I looked at it, it was gaining a lot of ground on unRaid, and because it runs on Windows I'm able to do a lot more with it. Like gameservers, and transcoding Blu Ray rips on the fly so I can watch them on my phone or whatever.