>i found that many large company's software (with VFP), still put on FOX logo at top left of window.
>how can i replace it for a company logo.

If you mean the icon, you need to create a .ico file with both large and small icon images in it, and specify that as the icon in the Project before compiling the application. George Tasker wrote a FAQ on this; it can be found in UT's FAQ section (click on the Purple Book to get to the knowledge base.)