I run windows on my macs, i use Vista Business edition, but it does not run well under Parallels due to its high memory demands so if your going with vista then run it under boot camp. OEM versions are supposed to be sold with new computers and therefore are a bit cheaper. If you really want to run Windows then get XP Pro, much more compatible with everything and runs excellent in both parallels and Boot Camp. I have been running Vista for about 6 months and to say it is disappointing would be the understatement of the year.