My previous post about this issue didn't got too many answers and it was kinda specific and hard to understand. I think I've managed to understand the problem better and I now believe it to be a Vista issue...
The problem lies on all types of fixed border styles like FixedDialog, Fixed3D, FixedSingle and FixedToolWindow. It does not happen on the sizable ones. This problem, like I said, it also happens only on Vista.
Let's say you have a form with any of the fixed border styles and set the starting location to 0,0. What you want here is for the form to be snapped to the top left corner of the screen. This works just fine if the form border style is one of the sizable options, if it's fixed, well, the form will be a little bit outside of the screen working area both to the left and top.
What's more strange about this is that the form location does not change, it sill is 0,0, but a few pixels of the form are still drawn outside of the working screen area.
I tested this on XP and it didn't happen, the problem is Vista specific. On XP, the only difference was the border size that change a bit between any of the styles. But the form was always perfectly snapped to position 0,0.
If possible, without finding how many pixels are being drawn outside of the working area and then add that to the form location, is there a possible way to fix or workaround this?