a little bleach in the pan helps keep the funky smell away too....

just a tiny amount will kill the creepy crawlies.

Also make sure your evap coil is clean and you keep the filter clean, as well as the condenser coil. And as said above, make sure the weep holes are clear, they are usually in the bottom.

Another trouble area is the slingers on the fan blade, if you grow fungus on them,(They actually go into the water and sling it on the condenser coil) it unbalances the blade and will make noise.

And before anyone gives you any crap, window units are by far the most efficient air conditioning system.