installing 64 bits version also installs 32 bits

When installing FlexCel in options I explicitly only checked Windows 64 bits version to be installed. No Windows 32 bits, and no FMX either. For developing 64 bits ISAPI dll I want to be sure no mix with 32 bits occurs. But to my surprise also 32 bits gets installed. Why?

The win32 build is always needed as it is used by Delphi itself (which is a 32 bit app) when we install the packages in the IDE. This is the reason you can't really unselect it.

But you shouldn't worry about mixing 32 and 64 bit dlls, as there is no way in Windows of mixing them. 64 bit apps can only call 64 bit dlls, and same for 32 bit.