I am searching for a listing of win32 API in certain "database"/XML format.

I'd require it to simply produce a "conversion layer" between win32 API and also the greater level language I am using (harbour/xharbour). Because this runs Pcode, it's important to change parameters to C standard...

Rather than doing manual code write, Let me automate the procedure...

just for instance, the home windows API definition (obtained from MSDN)

DWORD WINAPI GetSysColor(
  __in  int nIndex
);

ought to be changed in

HB_FUNC( GETSYSCOLOR )
{
    hb_retnl( (LONG) GetSysColor( hb_parni( 1 ) ) );
}

AFAIK, pinvoke.internet only stores text data using the PInvoke definition for that call. Not so helpful if what you would like is one thing for a pre-parsed database of APIs.

Most likely you can create an small parser which will go ahead and take include file and translate it to the thing you need. For the reason that situation, I'd recommend using lcc-win32's include files, because they are virtually body fat-free/no-Baloney version from the SDK headers (they do not include a lot of special reserved words you'd need to ignore, etc.)

Obviously, you've Microsoft Platform SDK, but it's in raw .h C code, so difficult to parse!

Similar work happen to be made by VB customers (and Delphi customers and most likely for many other languages), for instance ApiViewer has such database, however in some proprietary binary format (.apv extension), so you may need to reverse-engineer it.
Similarly, there's an API-Guide, that was located at Allapi.internet however the later appears to become a parking site now. It used .api files (again binary-proprietary).

Concerning the nearest factor I understand of could be: http://pinvoke.net/ Maybe they'd share their data along with you? There is a Versus tool that accesses this data, therefore it might be a webservice. You may even have the ability to sniff that out.