Toyota echo 2000 - airconditioner belt squeaking

Well the belt could be loose or the compressor may be seized.....or the belt may be old and squealing.

I have the same problem, but I'm pretty sure the obvious solution (got to try it first) of replacing the drive belt is not all there is to it. I already replaced the belt, but the squeaking did not go away. I think the problem is the AC compressor making the squeaking (possibly needs a new bearing). The other possibility is the accessory belt is squeaking (that belt is harder to replace). I replaced the water pump so I know that wasn't the source of the squeaking. A new drive belt is cheap and easy to replace yourself, if that doesn't work, one thing you could try is putting on the shorter version of the drive belt that doesn't turn the AC compressor, if the sound goes away, you know its the AC compressor, if it doesn't go away, its probably the accessory belt (down at the bottom).