How Can I Debug Windows API Functions?
If you want to debug a Windows API function that has NT symbols loaded, you must do the following.
To set a breakpoint on a Windows API function with NT symbols loaded
Enter the function name together with the name of the DLL where the function resides. In 32-bit code, use the decorated form of the function name. To set a breakpoint on MessageBeep, for example, you must enter the following.
To obtain the decorated name, see Viewing Decorated Names.