Using AppInit_DLLs Registry Key in Vista

The signing part is not in any build of Vista, and, as of today, to restore the AppInit_DLLs functionality there is one more registry key, named LoadAppInit_DLLs with the value of 1 that needs to be created for the other key to take effect.

For 32-bit apps on a 64-bit OS you need to set this value under HKLM\Software\Wow6432Node\...