>I would like to know what are the GUI design standards for windows development. I know for example Win XP use the Font Tahoma as standard.
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>But what are other standards such as font size, the size of buttons on a form, size of toolbar buttons, height of combo boxes and text boxes.
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>Is there any documentaion on this?

At www.msdn.microsoft.com, do a search for "Windows User Expirience". It's part of the MSDN library.