The problem with this code is that it will change the size of the form to 0,0,0,0. This is what I have added:
I'm afraid you're wrong - the original code works fine. The problem you are having is due to the final parameter, the wFlags value.
In your example you have it set to &H50 - this value indicates that the 5th and 7th bits are turned on (&H10 and &H40 respectively). If you look at the constants for SetWindowPos you'll see that you have the following set: