I have a 1998 chevy blazer and when I push the brakes there is a screeching sound, sounds like th e disc for the brakes, what can be causing this?

 

Sounds like your pads have worn down to the metal. Pull the wheel and inspect - if its making metal to metal contact it could ruin the disc.

 

Actually, there is a squeaker on the pads that will cause this noise when the pads have worn down far enough. They are there to prevent the pad from completely wearing out before you get around to fixing it. Basically they are meant to be annoying enough that you'll want to fix them.