Newegg has systems, without an OS though:Newegg NUC systems
When I bought my wife's laptop computer (Levnovo), I had to immediately reinstall Windows 7 due to removing the hard drive and replacing with a solid state drive. It's really not that long of an ordeal, and you don't have tons of junk from the manufacturer.
For a HT/normal computer, an I3 isn't bad. I'm using one now to run my HT system. I think if you want to do video processing, though, I'm not sure whether the HD 4000 (or whatever Intel calls this) is able to do a lot of that. If these computers lack anything for high-performance HT use, it's in the video department. However, I've been able to use my Intel I3 with HD 3000 with no problems, but I also don't use MADVR or any other video processing system.