With the release of Reaktor 6.4.1, there will no longer be a 32-bit version of the software.
What can I do if I want to keep on using Reaktor 6 in 32-bit Mode?
If you depend on using the 32-bit version of Reaktor for your work, do not install any Reaktor updates later than version 6.4.0. Doing so will uninstall your 32-bit version.
What do I do if I already use the 64-bit version of Reaktor?
Nothing. Previous versions of Reaktor installed both 32-bit and 64-bit versions simultaneously by default. When you run the 6.4.1 (or later version) update, it will also uninstall any previous 32-bit version that may have been installed on your computer.
Where can I find an installer for the last supported 32-bit version of Reaktor?
You can download the Reaktor 6.4.0 installer from here.