“Have you ever seen the rain (on your background image through a Delphi window)?” Ok, sorry to all the Creedence Clearwater Revival fans out there ;-). Today we wanna talk about how to achieve translucent Delphi windows with Windows Vista. I know this does not sound like a big deal for all the lucky owners [...]

This answer is very easy - just use GetWindowThreadProcessId
JWA declares it as followed:

function GetWindowThreadProcessId(hWnd: HWND; lpdwProcessId: LPDWORD): DWORD; stdcall;

The function returns an identifier (not a handle) and also may set lpdwProcessId to the identifier (again not a handle!) if it is not nil. Be aware that identifiers aren’t handles, so you must not close them [...]