My legacy will occasionally squeel the belt at startup. Seems to help if I minimize the electrical load (if I have the headlights on and the heater on full blast it tends to squeel a lot more often).

 

Definitely check condition and tension of the belt though.

My 2005 Impreza has made a horrible noise on startup since it was new when the temp is about 10 degrees F or colder. It doesn't sound like a belt, it sounds more like hydraulic fluid starvation. I always figured the PS pump was bad or going bad. The car has 83K miles on it now and still makes the same noise when extremely cold. It is no better or worse than it was when the car was new. While it scared me to death the first few times I heard it, I've started to regard it as "normal" for my car.

I tightened the Pwr Steering/Alternator belt. Took me 30 mins: 1. Remove the belt guards using 10mm and 12mm sockets/wrenches. This will "force" you to loosen the alternator pivot bolt. 2. Press into middle of belt to check how loose it is. Mine had about an inch of movement. Check this belt and the other belt for wear or any condition problem, since you are so close to it. 3. Loosen the lock nut--about half way down the shaft of the slider (adjuster) bolt. 4. Lube up all of the bolts while you are here. 5. Tighten the slider bolt one full turn clockwise, enough to make the belt only move about .25" when you press down on the middle of it. 6. Tighten lock nut. 7. Replace all belt guards. 8. Start car and test drive, do some tight full lock turning to test for squeals.

I just fixed this problem yesterday, it would squeal at startup. I had new belts installed when I had the T belt done in july. They stretched from break in. I tightened the power steering/alternator belt (very easy) and tried to tighten the A/C belt which was even looser. I actually had to remove the idler bracket for the A/C belt because the nut that you have to loosen on the idler pulley was rusted in place. Impacted off, cleaned the threads, antisiezed the nut and the threads for the adjustment rod, all is tight and ready to rock and roll!