This is my favorite thing to do on my computer. The hard disk is something that will always get a lot of files and folders that will just use it's space and sometimes they are completely useless.
The hard disk is the most important part of your computer because it's there that all information inside your computer is saved. If you take care of it, it will take care of you.
There are three things you need to do to your hard disk:
1. You need to clean it. This means deleting all the files just using space and being useless.
2. Organizing the hard disk. This means using defragmentation tools..
3. Preventing the same from happening again so soon. The hard disk will work fine just for a few weeks because it needs scheduled human maintenance.
1. First step is to manually remove files you do not use anymore. Do you have a big folder with movies in it? Pick an external hard disk and star uploading all the files to it. Do you have several GB's of music? Pick a Pen Drive and insert all music on it. Do you have a huge archeive of old document? Zip them and send them to another drive. In your hard disk you will need to keep just the files you are in need right now, all other files can be deleted from it or moved anywhere.
Doing this just manually won't take you very far, you need to do something else in order to keep your hard disk in full share. This is where the software comes. I recently found a great tool called Ccleaner where you can pick all the programs you want to be clean and also the register and Ccleaner will do it. This software is free I don't know why because it's too good and it can even clean your hard drive old programs cache and temporary files. The first time I run this program it saved me more than 5.86 GB of data so imagine how my hard drive was just with my manual cleaning.
2. Your hard disk will have several holes there left by the cleaning programs. It's your duty to clean all those holes or at least to move them somewhere else. Windows Vista default defragment tool is not good or fast enough for it. I recommend using Auslogics Defrag Tool to keep your computer in top hard disk shape. This tool is free so use it! The process will take several hours in a new computer with few files on it, but it's necessary so do not skip it!
3. Finally you need to prevent this from happening in a so close future. I mean you need to limit the number of programs you install on your computer, you need to set you browser to clean it's cache after each session and you must also get rid of software that needs installation and run only portable software.