With update 1.7.0 (Hydra) Hearts of Iron 4 requires a 64 bit version of Windows to run. This is per design as Windows and MacOS are starting to phase out 32 bit supported applications. If you are running a 32 bit version of Windows you will need to roll back to version 1.62 as this will still work for you but we do recommend that you start looking at upgrading to a 64 bit version of your OS as more and more of our games will become 64 bit in the coming months.
Hearts of Iron 4 is now 64-bit
