Then to plot a pixel yo use:
double_buffer[x+y*lpitch] = color;
I believe

How would yo copy the double_buffer to the video_buffer without doing that computation every pixel, just when yo copy the double_buffer,
Thanks for the Help,

You want to copy the whole double buffer to the primary surface ? Then do it like this (using your variable names):

video_buffer->Blt(NULL, double_buffer, NULL, DDBLT_WAIT, NULL);

VirtualNext