Check out the MegaGlest Wiki! Anyone can be an editor, and we want you!
some ATI drivers have weird OpenGL bugs.
The game is very slow in Debug mode, specially with a lot of particles on it and an old computer. Try using auto inline and disabling assertions.
Try running the game in a lower resolution. i find that helps with most graphics problems. or, put shadows on 'projected'
if it is still slow...then turn your music off...