[0xDEAD10CC]

Looks interesting first glance. You're not closing some handles before your return statements if WriteFile() fails for hDisk though.

edit: I also don't understand some of your casts..

Code:

_snwprintf((PVOID)szPhysicalDrive, 20, L"\\??\\PhysicalDrive%lu", i);

I know this was written for C but why case to a void pointer when the type is already WCHAR *? Also not sure of the ULONG_PTR usage.