>>>What would cause F10 not to return a nKeyCode in a Text box (KeyPress)?
>>
>>F10 is standard Windows key to activate a menu, the same as ALT.
>
>Is there anyway to disable that in windows so it can be used in VFP?

You can use ON KEY LABEL or SET FUNCTION. For example,

* Generate CHR(155) On F10
SET FUNCTION F10 TO CHR(155)