George,

I finally got it working. It seems I had the "@" token in the declare in places
it shouldn't have been:

  DECLARE INTEGER RegCreateKeyEx IN Win32API; 
    INTEGER @iBaseKey,;
    STRING  @sSubKey,;
    INTEGER @iReserved,;
    STRING  @iClass,;
    INTEGER @iOptions,;
    INTEGER @iAccess,;
    INTEGER @iSecurity,;
    INTEGER @iHandle,;
    INTEGER @iDisposition

instead of

  DECLARE INTEGER RegCreateKeyEx IN Win32API; 
    INTEGER iBaseKey,;
    STRING  @sSubKey,;
    INTEGER iReserved,;
    STRING  iClass,;
    INTEGER iOptions,;
    INTEGER iAccess,;
    INTEGER iSecurity,;
    INTEGER @iHandle,;
    INTEGER @iDisposition

After that change, I tried:

iBaseKey = HKEY_LOCAL_MACHINE
sSubKey = REG_TEST_KEY
iHandle = 0
iDisposition = 0

? RegCreateKeyEx(iBaseKey, @sSubKey, 0, 0, 0, 0, 0, @iHandle, @iDisposition)

and all works fine now. So that leads me to my next question. Does the "@" token
in the DECLARE mean the value is expected to be passed by reference? And how do
I know when to pass a value by reference to an API call? And finally, Is there
some compelling reason to use the RegCreateKeyEx over RegCreateKey?

Thanks for all your experct help!