DEP technology in Windows Vista prevents the execution of code in non-executable memory. Windows Vista system binaries, such as Windows Installer (Msiexec.exe), are executed with DEP enabled.
If the code for a Windows Installer custom action is incompatible with DEP, the Windows Installer process unexpectedly ends. An access violation occurs, and the custom action code is not executed.
Custom action code must be compatible with DEP. Windows Installer developers should test custom action code on a Windows Vista-based system that has DEP enabled. Additionally, developers should use Microsoft Visual Studio 8.0 or a later version to make sure that custom action code is compiled to be compatible with DEP.