can anybody explain me wht is this?d3d hal..what is the advantages of disabling it?

"d3d hal" is Direct3d acelererated by hardware (it runs faster by using CPU + 3D card)

and "d3d ref" is Direct3D acelerated by software (it runs more and more slower than "d3d hal" by using CPU to emulate effect of D3D scene)


There is no advantages on disabling it.

Generally games will let you choose which card you want to run them.  But for those few that don't want, you will need to disable the Voodoo 2 Hardware Abstraction Layer.
This way, you can switch the D3D support on and off and use your primary card for D3D games which don't offer the choice.
For that, you can use the freeware 3DControlCenter (3DCC) or Leinen's Voodoo2 Tweaker