I think the cheaper version is OEM (Hence only 64-bit) and the more expensive version is the retail box (64-bit and 32-bit). There are some other limitations with OEM, like after you install it on your computer, you aren't supposed to uninstall it and move it to different computer (I believe).
And with OEM there is no Microsoft support !
The cheaper one is oem, the difference is the oem you cannot call MS and get free support if you need it. That is the only difference.
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Oh I see, well I don't need their support Thanks for the help everyone!