It is always prudent to backup important data as a format will essentially
wipe your drive. If you plan to reinstall Windows XP, which I infer that you
want to from your question about backing up drivers, you'll find that XP
will most likely find your hardware during the reinstall. However some
devices might not be detected. For example your sound card or video card
might not have drivers on the XP CD. If this is true you will need to
install those after you've installed XP. Often computer manufacturer's will
supply CDs with their product at the time of sale. These generally have the
drivers required. However this is not always the case especially if your
system is older.
Before you format assuming your system is running install this freeware app
AIDA32
http://www.aida32.hu/aida-features.php?bit=32 and run it. Then look
in the Computer section's Summary. It will give you a breakdown of your
system's hardware and there are often links to drivers for your hardware.
Visit the sites and download drivers specific to XP for your devices then
burn these to CD. Follow the instructions here for how to perform a clean
install
http://www.webtree.ca/windowsxp/clean_install.htm As you see you
will be able to format prior to reinstalling.
If you simply want to format the drive then you can look at the instructions
here for How To Format
http://www.webtree.ca/windowsxp/repair_xp.htm