fyi: vista is just an operating systems just like xp. for powerpoint, it's an office application which is sold/to be installed separately.
if you just use powerpoint for viewing presentations, you may download a free copy from microsoft's website, it's called powerpoint reader. on the other hand if you need to create/edit presentations then you need the full powerpoint application which is bundled in office applications, you may consider microsoft office for that, latest version that is optimized for vista is ms office 2007.
there's also openoffice as suggested above, it's freeware and serves the same function as ms office, the equivalent application for powerpoint is openoffice "Impress".




