Your hard disk capacity should be a minimum of 6GB - I prefer to have much more disk space than you'd think you would ever use. It's kinda like closet space, whatever you have you still could use more. You should make regular backups or your computer system. Backing up your files could have you hundreds or thousands of dollars. It could save your job or mean the difference between staying in business or going belly up.
Computers can and do break, become mis-configured, get lost or stolen.
It is just a matter of time until this fact of life strikes you. Plan on it. A tape Backup system allows you to effectively copy the contents of your hard disk. A backup strategy is a must have for nearly all computers. Make it a Priority Item.