Advice, if you can afford it...
I have always bought the full-up version of Windows operating systems, despite the price. I can still use it for an upgrade, but if I have to flush the system, having only an upgrade disk is a hassle. In the old days, I'd have to install the old system first, then upgrade it. Don't know if that's still the case.
Now that Microsoft is supremely anal about putting the same OS on both my desktop and my laptop, this gets to be expensive. I'm still running Win2000 on my laptop, and XP on this machine. Now I wish I could remember where I put my nice new XP disk... #$@$%