Problem with K7S8X motherboard

Problem: the system doesn't boot. When there is only CPU on the
motherboard (I removed any other components from my system - memory,
graphics, sound cards etc. ), speaker beeps 3 times (indicates memory
problem, but so far there isn't memory installed, so everything is OK,
I thing). But after inserting memory in a slot the speaker is silent.
After adding a graphics card speaker still is silent and display
screen remains black. What could be wrong with my system? Could it be
that my memory is faulty or rather the motherboard is damaged

My system components
Motherboard: ASRock K7S8X
CPU: Duron 1600
Graphics: Riva TNT2 Pro
Memory DDR256MB PC2700