Most commonly used PC's today run a 64-Bit Windows on a 64-Bit CPU. However, most of the software provided is still 32-Bit. So is the Nero Suite. Microsoft Windows provides a compatibility layer that allows 32-Bit software to run perfectly well on 64-Bit. To determine if a software is 32 or 64 Bit you can check the installation folder. 32-Bit software installs into C:\Program Files (x86), whereas 64-Bit software is in C:\Program Files. On a typical Windows PC you will find that there are more entries in the folder with (x86) than in the other.
The drawback of such approach is a minimal performance difference (less than 5%). Plus 32-Bit software can only address a total of 2 GB of RAM. However our engineers applied a special technique to make it possible to address more RAM. You can easily see this in the task manager while e.g. exporting a complex timeline with 4k videos in Nero Video. Furthermore some very complex tasks, like HEVC decoding, also run in 64-Bit inside our 32-Bit software to ensure the best customer experience.