Hi There
As you have not stated that there is anything wrong with your computer I assume that you are being prudent and looking for a way to back things up before the worst occurs.
If so there are many programs out there that allow you to create an image of your system to CD or DVD or another partition and recover it when disaster strikes.

I myself use Norton Ghost which I find very reliable.

If you dont want to shell out for Norton then I would go into the newsagent and look at the PC magazines as they sometimes have free backup programs on them in March Computer Shopper had Drive Copy and on the October edition of PC pro they had Titan Backup. I think these are only good for copying from one hard drive to another.

Another way I would recommend is to copy an image again using Norton or some other software to an external drive via USB or Firewire, this method is the one I prefer as before I have backed up to CD and when I have come to restore them they dont seem to want to restore correctly also if the image is on a partition on your hard drive and your hard drive fails you loose all your system and data.

if you do decide backup to CD you need a way of trying them out before disaster strikes.
Hope this helps
Kindest Regards Tony B.