@Terrificli @Soulfox -- that's good advice for general maintenance, but what about the root problem of seriously running out of hard drive space? If you are nearing the limits of your hard drive capacity, cleaning out temporary and junk files will help but it won't solve the underlying problem.
The good news is that hard drives are cheap. Adding a new, internal drive is a very easy operation and most desktop computers already have a spot and the wiring in place to install the thing in minutes. Just spend a few bucks, throw in a huge hard drive and that will solve your problem.