Is it important that you get a desktop computer with Win 7? Laptops in today's environment may work out better if you are traveling and you want to keep in touch.
I upgraded my desktop from XP to Win 7 and my laptop also. I take the laptop with me on all our trips from a weekender to a multi-week cross country.
At home, both computers are linked and I can use one to process files from the other. Only the laptop has a printer connected, so the desktop uses it as a network printer. Win 7 has worked very well in this environment.