Instead of defining a new window, you can probably maximize the default preview window and achieve the same behavior:

KEYBOARD "{CTRL+F10}" && force preview window to maximize itself
REPORT FORM MyReport PREVIEW

>Hello,
>
>For the previewing of reports I want to define a window (DEFINE WINDOW) which has the size of the VFP screen. The problem I have is how to translate the _SCREEN.HEIGHT and WIDTH properties to the window size.
>
>Any ideas?
>
>Thanks for your help in advance.