I have a new HP Pavillion computer - 6gig ram-AMD quad core. After installing several programs, i.e. itunes, the system will not reboot.
If you'll notice I bolded in the quote itunes. Making an assumption here that itunes could be causing your problems.
Reasoning behind the assumption is that when I first got my desktop with Vista Home (32 bit) just over a year ago, I installed itunes and had nothing but problems. Once I uninstalled it, it was better but just wasn't the same. Now that I've done a clean Vista install and no installation of itunes, everything works together nicely.
Later discovered that itunes just doesn't like to work well with Vista. Even though it has been updated and supposed to work with Vista, it just doesn't like to "play nicely" with it. itunes does seem to work well on XP though.
I'd suggest that if you haven't done a reinstall yet, first try to uninstall itunes and see what happens.
If your going to try reinstalling again, I would suggest you don't install itunes and see what happens.