From CCRMA Wiki
Installing PlanetCCRMA on your PC is not quite a labor of love, but it does take some attention. Most are coming to this process with a Window's Installation currently on their PC, so we'll take that assumption here.
Backup Your Data
You must have a backup of your data! What kind? The answer to this question will do it... "To what extent should I backup my data such that if I lose my current partition and my data is lost, will I not have an emotional reaction?" This answer to this question and what you choose to do about it is entirely your responsibility.
Here are some helpful links for Windows users: