It is recommended to use 64–bit version of any Cortona3D tool on x64–based operating systems. 64–bit version of the tool allows working with bigger geometry by utilizing more available RAM on your machine.
64–bit installer includes both 32 and 64–bit versions of the product.
The version of your Operating System can easily be checked by right–clicking Computer icon and selecting Properties. "System Type" indicates the version of OS (see screenshot below).