There are many ways to free up space and many programs that will do it for you. Basically if you go down this route then your looking for Cleaner Programs like "CC Cleaner" However i recomend that you upgrade your Hard drive to 120Gb plus. a 320Gb laptop hard drive will only set you back £80 then you dont have to worry about space for a while, you should still clean out old files etc. Changing your hard drive is not difficult but you need to know if it is ATA or SATA Laptop hard drives are 2.5".
Opening is not that difficult but if you need a guide then you can check the Video Tutorial on how to open Laptops at: Home
It is quite an educational video even if you just use it to replace a hard drive.