Dell used to supply actual CDs if you called or emailed them. Manufacturers do not tend to include them at all these days.

I agree about double-checking the power supply. I never directly test them. I use a substitute, and see if the computer runs. Power supplies aren't very expensive, but also don't seem to be all that reliable. I go through power supplies faster than any other computer part, except perhaps disk drives.

Windows 7 Professional or Ultimate is the best that MS has to offer for a client OS. The server version is called Windows 2008 R2, and comes in a number of configurations that most people will find just plain confusing.

I don't buy boxed computers at all. I also don't buy operating systems, at least not directly. As an MSDN licensee, I can run 10 concurrent copies of each flavor of MS operating system (plus a whole lot of other MS products). I have no idea what the MSDN license costs, as my work pays for it.