Turns Over But Won't Start, It's A 2001 Chevy Blazer, What's Wrong?

2001 chevy blazer won't turn-over, battery was tested good two weeks ago. Initially it would not start but would make a high pitched steady noise.  Today when I turned the ignition key nothing happened.  The electric system seems fine, fan, radio, lights etc... Are working. It won't crank, turn-over, or click

Bad module in distributor

First you have to determine if it is fuel or spark that you are missing.
If it's got spark and fuel, then compression would be the problem.
I would guess, fuel or spark would be missing.
If lack of compression, were the problem, the engine would be spinning freely.

Might be your ignition switch.  Happened to my 1997 Blazer.