I just bought a 2002 Impreza WRX wagon, manual transmision, today after sitting in the drive all day it is making this squealing sound. It is the worst right when you start up and are taking off in 1st, after that it seems to come and go at varying volumes. Coming to a complete stop and taking off again does not seem to make it act up again but it can be heard through all different RPMs and in all gears up through 4th, (driving it in the city, didnt get up to 5th gear speeds, not sure if sound will continue). It does not seem to be specifically when releasing the clutch accelerating or turning, its just kinda always there.
I am mechanically inclined but I have never worked on cars before. I would guess, start by checking all the fluid levels, but after that I am at a loss.