I've never had Windows 7 take more than about 30 seconds to load, even on a very old computer. So if it goes more than a minute I'd say you probably have a problem. The "loading" bar in XP really wasn't a diagnostic tool. It was just there to make people think it was busy, and I've seen computers lock up completely during the loading process but the "loading" bar was still happily scrolling across the bottom of the screen.