I don't know your computer specs but I'm currently running 4x AGP on an Athlon 600@630, Asus K7V, 128MB Ram, Creative GTS2, SB Live & Win95OSR2.
It's not easy to get 4x AGP running stable, it took countless hours for me to troubleshoot.
Disable your soundcard first to check for conflicts. If not, check your AGP drivers, viagart.vxd ver 3.56 works the best for me and gives the highest 3DMark. The 4.03 version was unstable on my system.
"Believe me! The secret of reaping the greatest fruitfulness and the greatest enjoyment from life is to live dangerously!"
Friedrich Wilhelm Nietzsche