You deleted everything from your USB key or a drive, so there should be enough free space to copy the new files, but you still get the not enough free space message in Mac OS X? This is what you need to do.
You created your own movie in iMovie but you can't figure it out how to save the darn thing into a playable .mp4 file on your hard drive. I've been there, let me show you how to do that.
VirtualBox is a great free cross-platform virtualization program that enables you to run Windows, Linux, Mac OS X and other operating systems on you Windows, OS X or Linux computer.
If you want to make a clean install of the new OS X Mavericks or even the older versions of Mac OS X, than I strongly suggest you to create a bootable OS X key or a drive.
If you are more of a visual person and would like to organize your folders and files using different colors, than check it out how to use color labels in Mac OS X.
We have already learned how to create a bootable OS X Mavericks USB drive using a third party app, this time I will show you how to create one directly in Mac OS X.