Assuming they are all the same type of machine, I would just set up a clonezilla server. http://clonezilla.org/
I did that for a bunch of machines at my high school. Make one master image, upload it, and then push it via PXE to all the clients. I was using my home desktop, so I could only do about 12 machines at once. I had 100 machines to do. It took about 2 days to do them, but I was also working on other projects in there so I bet you could cut that time down quite a bit. Hope this helps.