How do I get a dual monitor Matrox Millenium system to not split dialog boxes across the screens?

A. A. Perform the following:

1. Start the registry editor (regedt32.exe)
2. Move to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\mgax64\Device
3. Double click User.CenterDialogs.
4. Change from 00000000 to 00000001
5. Click OK
6. Close the registry editor
7. Reboot the machine

From the release notes this no longer works in 4.0 but does for 3.51 systems.