Yes, you can!
In Windows, there is a single Reason installer containing both the 32-bit and the 64-bit version. When you run the installer, it detects if you’re running a 64-bit OS, and automatically installs the 64-bit version of Reason. Otherwise, the 32-bit version is installed.
It might be desirable to run the 32-bit version even under a 64-bit OS (for example if you’re using Reason with ReWire and a host that only supports 32-bit ReWire). Then, you can force the installer to install the 32-bit version in the following way:
Forcing a 32-bit installation this way should give the name “Reason (32)” to the desktop icon and Start menu folder.