Sorry, unlike PlayStation 1 emulation, you're required to get a 3D video card if you want to even play any Nintendo 64 game, because if you don't have a 3D video card, it's probably gonna be no faster than 5 FPS.
2 solutions:
1st) Use existing OpenGL plugins with Mesa3D - slow (http://www.mesa3d.org)
2nd) Use Hacktarux SOFTWARE rendering plugin - low compatibility iirc (http://sourceforge.net/projects/mupen64-gfx - you gotta checkout the CVS becuase there is no release I think)
2 solutions:
1st) Use existing OpenGL plugins with Mesa3D - slow (http://www.mesa3d.org)
2nd) Use Hacktarux SOFTWARE rendering plugin - low compatibility iirc (http://sourceforge.net/projects/mupen64-gfx - you gotta checkout the CVS becuase there is no release I think)