Hi Al,
Almost got it this time :) You should be checking that pParameters is not NULL, not &This->createParms. Note that if This is not-NULL, &This->creatParms will be not null as well since you are just getting the address of a struct. Also on failure, according to MSDN, you shoudl be returning D3DERR_INVALIDCALL not OUTOFVIDEOMEMORY.
Probably the following would be most correct:
I've patchified Aric's corrections. That's what I get for not doing any C/C++ for 5 years ... I'll remember to check MSDN as well next time for the return code - I just scanned the rest of the file and saw a lot of stuff returning OUTOFVIDEOMEMORY.
-Al