opengl can not arrive at the max size of client area of window .

i have programed with opengl in Vc++6.0 . i have setup the pixelformat as most popluar sate. my computer is notebook pc(Dell cpx),
but i found that the program can not make use of all of client area of the view window.
satement as following ndraw(){glclearclolor(
1,0,0,0);glclear(…).after every 7 times to restart my program,the program can make use of all client area,but,in the rest of times ,the boundary of area cleared by opengl statement have some distanc to boundary of frame window.i have puzzled by the quenstion some days, who can help me ?
thank you!!
i am a chinese ,my english is no good .please pardon me.welcome to china.

Mostlikly you are not setting the viewport correctly (if at all).

You should ask questions about OpenGL programming in the developer boards.

Hope that helps.