SetViewport problem

hello,everybody! i have a problem when setting viewport BackBufferWidth=1024; BackBufferHeight=768; D3DVIEWPORT9 myviewport; myviewport.x=0; myviewport.y=96; myviewport.width=1024; myviewport.height=576; myviewport.MinZ=0.0f; myviewport.MaxZ=1.0f; g_pd3dDevice->SetViewport(&myviewport) i want to make my app look like a wide-screen movie,something like this: ******************************************* ******************************************* ******************************************* ******************************************* ******************************************* ******************************************* my render state:(i am rendering point sprite using Fix Function Pipeline) D3DRS_ZENABLE TRUE D3DRS_LIGHTING FALSE D3DSAMP_MINFILTER D3DTEXF_LINEAR D3DSAMP_MAGFILTER D3DTEXF_LINEAR before rendering pointsprite: D3DRS_ZWRITEENABLE FALSE D3DRS_ALPHABLENDENABLE TRUE D3DRS_DESTBLEND D3DBLEND_ONE rendering sprite: D3DRS_POINTSPRITEENABLE TRUE D3DRS_POINTSCALEENABLE TRUE D3DRS_POINTSIZE 1.0f D3DRS_POINTSIZE_MIN 1.0f D3DRS_POINTSCALE_A 0.0f D3DRS_POINTSCALE_B 0.0f D3DRS_POINTSCALE_C 1.0f after rendering pointsprite: D3DRS_POINTSCALEENABLE FALSE D3DRS_ZWRITEENABLE TRUE D3DRS_ALPHABLENDENABLE FALSE i set only one viewport,and the top and bottom area(which i didn't take care of) sometimes flash between black and the back image of my application window. the sprite could be rendered correctly in the viewport i set i am not sure if i described this correctly,i captured a few pictures of my application but i don't know how to post them here.