Farhad-

>Please guide me about GUI design books or other resources, We are programming in VFP 7.0 .

There is the Windows Interface guidelines book (http://www.amazon.com/exec/obidos/ASIN/1556156790/qid%3D1003422972/ref%3Dsr%5F11%5F0%5F1/103-4329830-1226202).

Also, some people really like Alan Cooper's book, "About Face: The Essentials of User Interface Design," though I'm not a huge fan.

If you search on Amazon for user interace guidelines, you'll find lot's of choices, too.

I wouldn't minimize the value of your own experience either (and your colleagues). By that I mean, keep a log of interfaces that your users have liked, and disliked, and why they liked or disliked them. Also, before you decide on a book that will represent your standard, identify who your users are. Are they heads down data entry? Or anonymous kiosk users in a public place? That will all impact the appropriateness of any interface guideline.