FS9 will work in either 32-bit
or 64-bit versions of Windows, and is compatible with Windows versions from Windows 98 through Windows 10.
IIRC, a 32-bit program such as FS9.exe can be run in
64-bit Windows on a computer with at least 5 or more GB of physical system RAM modules reportedly can be allocated up to a full
4GB of User Virtual Address Space (aka "USERVAS") for that FS task session
after FS9.exe has had the "
LARGE_ADDRESS_AWARE" flag applied using the above cited 4GB Patch from NTCore.
Users of
32-bit Windows can can be allocated up to
2.65 GB of User Virtual Address Space (aka "USERVAS") for that FS9 task session
after FS9.exe has had the "
LARGE_ADDRESS_AWARE" flag applied using the above cited 4GB Patch from NTCore,
and when the "/3GB switch" and "USERVA" of 2560MB is
also configured in the Boot.ini file for
Windows XP.
https://msdn.microsoft.com/en-us/library/windows/hardware/ff550245(v=vs.85).aspx
Note that in
32-bit Windows Windows versions since Vista and later, "
the boot.ini file has been replaced with Boot Configuration Data (BCD). This file is more versatile than boot.ini, and it can apply to computer platforms that use means other than basic input/output system (BIOS) to start the computer."
http://windows.microsoft.com/en-us/windows/what-happened-boot-ini-file#1TC=windows-7
Hope this helps !
GaryGB