i was planning on buying vista ultimate so that when i buy my macbook i could use windows software and play games via bootcamp. but i realized that vista is really expensive so i searched online and sure enough i could just get the home premium edition. i searched this website http://software.pricegrabber.com/windows-operating-system/m/32269562/search=microsoft%20windows%20vista%20home%20premium%2064bit/st=product/sv=title/ and it all lists as oem and not the retail box version of vista home premium 64bit. i was wondering if there's something different with oem version and retail version. cause i need 64 bit because im planning to put in 4 gb of ram. thank you.