Call of duty demo troubles

I try to open the demo but it pops up with this message

…WARNING: could not set the given mode (4)
…setting mode 4: 800 600 FS
…using colorsbits of 16
…calling CDS: ok
…created window@0,0 (800x600)
Initializing OpenGL driver
…getting DC: succeeded
…GLW_ChoosePFD( 16, 16, 0 )
…35 PFDs found
…GLW_ChoosePFD failed
…failed to find an appropriate PIXELFORMAT
…restoring display settings
…WARNING: could not set the given mode (3)
…shutting down QGL
…unloading OpenGL DLL
----- CL_Shutdown -----
RE_Shutdown( 1 )

Hunk_Clear: reset the hunk ok
GLW_StartOpenGL() - could not load OpenGL subsystem

Im not good with computers so could you explain to me how to fix this in lamen terms!!!

hey man, dont post error mssg’s, they wont help u or anybody. try

The demo only supports Nvidia Geforce (or better) and ATI Radeon 7000 (or better) 3d cards with the latest drivers installed.