Things have changed
Lets correct that then. If you bought a PC with Vista (which certainly wasn't a Pentium 3), it can run 7.
For what the average home computer is used for, there's not much improvement in a new box. I've also noticed a trend. Power users such as us are more frequently taking the guts out of our old boxes and building a usable rig for Mom and other friends/family, rather that throwing it in the attic or getting rid of it. While I'd often piled up parts for servicing, I'm building complete systems out of pieces and parts much more often, as the components aren't obsolete as fast. Perfect example is a DVD burner. Remember in the days of CD burners how often the speed increased 2x, 4x, 16x etc.? 5+ year old burners are still fine if you don't mind the cables.