You should create a Acronis bootable disc.
You then back up the image of your partition, or "C" drive to either a different drive, or partition, or CD, DVD.
Then if you get a problem, you can boot the computer with the Acronis boot disc, then once it is running, remove the disc and put in your CD, or DVD disc containing the image.
Ideally you would use a DVD, as it would take a lot of CDs to backup XP and your data.
Remember that restoring an image, overwrites all the information on the drive, or partition you restore it to. You end up with an exact copy of your computer, as it was when the image was created.