Hard drive issues? wastes too much memory?

Your OS and your own files will total 40 to 50 GB depending on OS. There are hidden system files, recovery point files, backup files from updates and a page file (the area of disk used by memory to hold data while it does other work, then call it back as required) which a search will not see. These can easily account for the rest of the used space. uming you have Vista the OS can be more than 20 GB