Firstly, it's not usually necessary to reformat a hard drive in order to reinstall Windows. An 'on top' installation will fix most problems. You should always try it first, since such an installation preserves all your program and data files, including all your drivers. (I've done an 'on top' installation many times, both on my own PC and on other people's machines. It nearly always fixes any problems. The only software I've ever had to reinstall has been the anti-virus program. I've never lost any data files, such as Word documents or images).
Depending upon how the BIOS on your PC is configured, you should be able to boot it up (without accessing drive C) by restarting it with either an original Windows disk in the CD drive or a boot disk in the floppy drive. (You can use a Windows 98 or ME boot disk, which can be downloaded from the internet, since the version of Windows is irrelevant at this stage). If neither of these options work, go into the BIOS to change the order in which your PC looks for a boot disk. (The key you need to press, to enter the BIOS, should appear in the on-screen information when you first start the computer. It might be F2, F8 or Delete).
With a Windows XP OS disk in the drive, you simply need to type C:setup to start an on top installation. If you really want to reformat the drive first, type C:format
As CF indicates, a 'clean' installation of Windows will lose all of your drivers. This frequently means that your PC will only boot into 640 x 480 graphics mode until you reinstall the graphics driver.
To back up your drivers, you could try using Driver Genius. The program's features are rather limited during the 15 day free trial period but they should be sufficient for your needs:
http://www.driver-soft.com/
Chris