"Windows 7, or Windows 8 Adobe® Premiere® Elements Editor runs native on 32-bit and 64-bit operating systems"
Click the BUY button on the right side of the screen
What you download from Adobe will depend on your computer operating system.
If you have Windows 7 64 bit, Windows 8 64 bit, or Mac 64 bit, then the downloaded Premiere Elements 11 will be a 64 bit application that can take advantage of the 64 bit system resources.
If you have other than those operating systems, the downloaded Premiere Elements 11 will be a 32 bit application, even in a 64 bit system. In the latter case, the 32 bit application will run in the 32 bit compatibility mode of the 64 bit system with all the resource limitations of a 32 bit system.
Please let us know if you need clarification on anything that I have written.
I would suggest that you download the tryout version of Premiere Elements 11 before purchase to make sure that it performs OK in your computer environment as well as meets your expectations feature wise. With the tryout version, instead of BUY, you would use the Continue Tryout up to the 30 days.