I have tried everything I can think of, on all three of my systems (2 XP Pro, I Win98), to duplicate your taskbar (yes, that is the ?official? Microsoft name) problem; I cannot.
Windows normally adjusts the program window size automatically so that none of it is hidden under the taskbar, at least for all well-behaved, Windows-compliant programs. You should not need to restore it and set it to a smaller size as previously suggested.
I could get the taskbar to hide the program window title bar, but only temporarily, under the following conditions:
1. Have a program window open and maximized.
2. Have the taskbar on the bottom of the screen.
3. Have the taskbar properties set for both ?auto-hide? and ?keep taskbar on top.?
4. Move the taskbar to the top of the screen and immediately lock it ? never moving the cursor off of the taskbar.
Under these conditions the Taskbar will not auto-hide when the cursor is moved away; thus, it will block the program title bar. However, if I click anywhere, the taskbar will hide, and will behave properly after that, appearing only when I move the cursor to its edge of the screen. If I do not lock the taskbar, it behaves normally from the start.
If the auto-hide property is set to off, the program resizes immediately after the move, so that the title bar is always visible.
I wonder why you lock the taskbar? I keep mine hidden on the left, and unlocked. I have never accidentally moved it, so I never lock it. If you worry that someone else will move it, locking is little protection; they only have to unlock it and go ahead with the move.
I suppose some programs could specify their window such that it would override the Windows automatic resizing, and part of the window would then appear under the taskbar. However, I have not encountered any such program.
Please let me know what taskbar settings you are using, and the program(s) involved when you encounter this problem. I would like to research it further.