just get a new belt already scrooge

(without AC - i.e. water pump running on the ribbed belt you can take it off to test if its the p/s belt but the sound it almost with no doubt just that)
5£ and you can change it in 5 minutes... not worth squirting wd40 on.
put steering wheel to full right lock... then you dont have to jack it up unless it's lowered
lock at the p/s belt, you'll see a nut on the p/s pump with a bolt in there (no 3). loosen that bolt a bit.... don't turn the nut yet.
loosen nuts/bolts 1, 2, 4

turn the big nut at no 3.... take belt off, put new one on... put it tight (should be able to still push through for a few cm)... run engine for a short while, recheck tension, do bolts up - done