I just received my new 27" i5 iMac a couple of days ago and I'm wanting to use boot camp for Windows 7. I'm new to the mac scene so my question is do you have to purchase the retail version of Windows 7 or can you use the OEM (system builders) version like is here: http://www.newegg.com/Product/Product.aspx?Item=N82E16832116754 for bootcamp? Also, should I get the 32 or 64 bit version? I will mostly be using Windows 7 for gaming (steam). Thanks for the help!