re-posted: Its if you have WinXp or anything above Windows ME where you can't create a startup disc any other way:
Put a floppy disc into the floppy drive, go to my computer and right click the A: drive (the floppy drive) and go to format. Format the disc. (follow the instructions below to get it to have it as a bootup option before the hard drive after setting it up)
CREATING A BOOTDISC
Go to http://www.bootdisk.com/bootdisk.htm
and download the XP quick quick boot disc and unzip them using the windows unzipper. Then place these onto the floppy disk. I you have any other windows versions, download the appropiate one.
Restart the system, but now you'll have to make sure that it is set to see the floppy drive first
SETTING UP BIOS TO BOOT FROM FLOPPY
Go into bios (usually by pressing del at bootup). Make sure that in the first menu i think, the first boot device is set to the floppy drive, the second to maybe the cd rom drive, and the 3rd to the hard drive.
Now save and exit
You are now set. It will notice the floppy disc in the drive and start to boot it because those files make it a boot disc. After all the loading you'll be left with this flashing on the screen
Type this to access the C drive:
Now it should create a new line saying C:\ (or your main drive with windows on it)
Type this after it:
format c:\ (or the drive letter your windows is installed on, most likely C)
it will say, are you sure? you type 'y'
It will now do it, and after it has finished, you'll be able to place the win xp disc in and install it
Hope this works (Sorry about the long post, i'm sure it's worth my time though