I am trying to write to the registry. I can create a key, but not a value. can someone tell me what is wrong with this code?

Code:
                HKEY hkey;
		DWORD dmDisposition;
		
		RegCreateKeyEx( HKEY_LOCAL_MACHINE, TEXT("Software\\My Company\\My App"), 0, 0, 0, 0, 0, &hkey, &dmDisposition );

		DWORD dwType, cbData;
		BYTE m_dwMaxFileSize;

		dwType = REG_SZ;
		cbData = sizeof(REG_SZ);

		RegSetValueEx( hkey, TEXT("MaxFileSize"), 0, dwType, (PBYTE)"hi", cbData );
	
		RegCloseKey(hkey);