Ok guys I've got the most annoying problem. I've replaced the serpentine belt on my 97 blazer still squeaks. replaced the idler pulley, tension pulley and also have a brand new alternator on it. Still squeaks any ideas on what it might be.

The first thing I would recommend is finding a can of "Belt Treatment" spray or some sort of silicone spray. You want to spray first the AC pump and then the Power Steering Pump. This will usually temporarily shut it up and help you pinpoint the problem. If this does not seem to help spray around the water pump, as that is a common source of agony when it comes to squeaking.

Another way of finding the culprit is to get a long solid piece of metal like a prybar or screwdriver. Press the metal end to the pulley, and listen through the handle this is surprisingly very effective in most cases. Being that you replaced the tensioner and belt you can easily rule out loose belt. My hunch would be water pump or power steering. Good Luck, let me know how you make out.