OK you need to do a disk cleanup first. Because we don't know your operating system XP, Vista etc you can find it in... start button, all programmes, accessories, system tools disk cleanup. Then after you have said 'yes' to clean it all. You need to check the space left on you hard drive. So go to Computer and click on the HD. Depending on your platform (Vista, XP) you will probably need about 10-15% of free space to perform a defragment. If you don't have this space then you need to delete enough files (films, videos, music etc) to create that space then go to system tools and defragment. If you cant find it then do a windows search for defrag an it will show up. Using XP turn off your screensaver and have no programmes running in the background. Vista not so much a problem. Either way it can take a few hours to complete depending on the size of the drive and the amount of fragmentation.