Ok, first off, what Operating System are you running? Secondly, is this a Laptop or a Desktop? Thirdly, Do you know if you have one physical Hard Disk Drive, or multiple? Fourthly, how much Random Access Memory do you have installed?
In best practice, you should free up room on your C:\ drive partition. Delete obsolete files such as cached web pages, things in your Downloads folder that you do not need anymore, etc.. I always recommend that people use a small and fast drive for their Operating System and a separate physical drive for their stuff, like documents, music, games, etc.. Laptops do not always allow for this configuration, in which case I recommend an external drive for backups and things that you do not need access to all of...