See also http://www.adobe.com/products/premiere/faq.html#64bit-support
"I use a 32-bit version of Windows and want to purchase CS6 Production Premium or Master Collection. What should I do?"
On Windows, the CS6 versions of Adobe Premiere Pro, After Effects, SpeedGrade, and Encore require a 64-bit edition of Microsoft® Windows 7.
If you are using one of the following operating systems, you will not be able to install or run those applications:
- 32-bit and 64-bit editions of Windows XP Home or Professional
- 32-bit and 64-bit editions of Windows Vista® Home Premium, Business, Ultimate, or Enterprise
If you are using one of the listed incompatible operating systems, Adobe recommends that you upgrade to a 64-bit edition of Windows 7 Home Premium, Professional, or Ultimate.