If you compile the Delphi application using the /LARGEADDRESSAWARE flag, it will be able to address the full 4GB on a 64-bit OS. Otherwise, when running in a WOW32, the OS assumes that the app is expecting the same environment that it would have on a 32-bit OS which means that of the 4GB of address space, 2GB is dedicated for the OS and 2GB is allocated to the application.