Hi Sara,

First off, you can can install the 32-bit version(s) of Radiance on a 64-bit Windows, OS, no problem. We only started offering 64-bit Radiance binaries for Windows with the latest packages (latest package, in fact: 5.0.a.3).

Second, you're welcome to use Radiance 5.0.a.3 with OpenStudio 1.7.0; the newer version works fine and we will likely bump up the recommended version number to this release soon. Despite the lack of official guidance to that effect, 5.0.a.3 works fine, probably better than 4.2.2 in fact.