Anyway, since he doesn't have the receipt for it (it was purchased some time in December by his company), is it still possible for me to buy Microsoft Complete for it? Also, any idea how the warranty would work without the original proof of purchase?
When I went to register it online I had an opportunity to purchase MS complete which I didn't pass up. It's super simple and I don't think you'll have a problem with it.
Just don't drop it pulling it out of the box. No joke it's happened to several people here.