> BTW, that number is based on most monitors these days running at 70hz, and is a guess on my part (supported by some testing). I'm assuming that Windows sends a WM_PAINT message to all displayed windows immediately after the VBI.

I don't think that the vertical refresh rate of a monitor is related to Paint events. The former is a hardware "repainting" performed by the video card. The latter is a software event that occurs when a form or toolbar is repainted. A form or toolbar is repainted when part or all of the form or toolbar is exposed after it has been moved or sized, or after a window that was covering the form or toolbar has been moved. Using a Refresh method in a Resize event forces repainting of the entire object every time a user resizes the form or toolbar.