one possible cause of losing hardware acceleration by changing to a higher resoluition is youve used up the cards onboard vidmemory
eg it takes way more memory to store the info for a 1600x1200x32 window than it does 1024x768x16. more than 4x as much memory in this case in fact.

>>As I know, OpenGL is not support all graphic modes.
How can I get OpenGL supportable graphic modes<<

ok i understand this now, opengl does support all resolutions+colour depths any that aint supported eg 32bit colour on a voodoo3 are due to the card not being able to do them and not opengl.
ie if directx can support a certain resolution/colour depth then opengl can support the same