64-Bit Custom Actions
On 64-bit operating systems, Windows Installer may call custom actions that have been compiled for 32-bit or 64-bit systems.
A 64-bit custom action based on Scripts must be explicitly marked as a 64-bit custom action by adding the msidbCustomActionType64BitScript bit to the custom actions numeric type in the Type column of the CustomAction table.
|msidbCustomActionType64BitScript||0x0001000||4096||This is a 64-bit custom action written in Scripts.|
Custom actions based on Executable files or Dynamic-Link Libraries that have been complied for a 64-bit operating systems do not require including this additional bit in the Type column of the CustomAction table.