The most important factor here is BACKUPS! You must backup your important data - bottom line. Any important data (Word docs, pictures, music, home videos, etc) should be backed up immediately after creation. In the event of a failure (computers crash, hard drives fail, Windows becomes unstable, etc), you will have your backup copy, preferably on a CD/DVD, thumb drive, or external hard drive. These hold the most data, are very convenient, and reliable. Floppy disk is OUT! In a pinch you could use your floppy drive, but I do not recommend it. They are considered old school dinosaurs now =)
With a good backup, your PC can normally be restored to factory settings (worse case), and all your data can be restored in no time! Also, in an emergency situation, your backup may be used on another PC and you can get that project finished in no time flat!