Back Up Entire PC

I am a computer fossile having grown up with the teletype terminal and know almost nothing about todays computers. I finally bought a pc (my first) about 2 years ago. It has all of the software installed but I have no hard cd for any of the programs. There are a lot of programs and files.

I would like to backup everything in my computer on cd but am clueless.

The pc is a compac presario with a cd/dvd burner running windows xp home edition.
Where do I begin and what do I do?