The reason shaders won't work is due to the fact that your graphics card can't handle them. Try setting the other visuals settings to 0.
"Call yourself alive? I promise you you'll be deafened by dust falling on the furniture,
you'll feel your eyebrows turning to two gashes, and your shoulder blades will ache for want of wings."
it means that your computers can't handle shaders. Get a better grpahics card. I suggest a 'nvidia geforce' something.
EDIT: Andrecova got there first......
Nvidia Geforce 6600 and over can handle shaders with a decent framerate (around 20-30 generally, without Frame Skipping and all other features enabled.)
I don't know if any card before the 6600 can handle it.
(15:43) <Drakhir> Zaarock: everything is useless.
(15:43) <Blam> Drakhir: Including your penis
Hawkinz raised an interesting point, that being that shaders require OPEN GL 2 support, which isn't normally required for games.
"Call yourself alive? I promise you you'll be deafened by dust falling on the furniture,
you'll feel your eyebrows turning to two gashes, and your shoulder blades will ache for want of wings."