This is something I have with all the computers that I have, When you go to the advance control the Treble and balance are grayed out, I have the sound drivers in and the sound works, and I like to get this fixed as the sound on this computer needs all the help it can get
Iam have a Dell latitude d630
I have never heard of a way to activate the controls. I "think" that the Sigmatel chips used in the Dell laptops did not have the feature, but I could be wrong.
As a workaround use the eq controls in your music player application. For example in Windows Media Player look under Enhancements>Graphic Equalizer..