WARNING: Do not attempt this unless you know exactly what it will do to your computer. All information on your hard drive will be lost and unrecoverable!
So, you want to reinstall your operating system on a hard drive that already has one on it. The best way to do it is to delete the entire boot sector before partitioning and formatting the drive. First you will need to create bootable floppy disk. Mine has the following files, which I copied from a 95/98 computer:
Autoexec.bat, Command.com, Config.sys, debug code.txt, Debeg.exe, Di.log, Drvspace.bin, Ebd.sys, Edit.com, Fdisk,exe, Format.com, lo.sys, Mscdex.exe, Msdos.sys, Sjcdapi.sys, Sys.com, Vide-cdd.sys
Although you won't need all of these for deleting the boot sector, having them will make a good boot disk for future use.
You will next need to set your computer to boot to the floppy drive, if it isn't already set to do so. You'll have to access your Bios, which is usually done by hitting <del> or <F1> during start up (yours may be different - it should say on the screen). If you don't know how to play with the Bios, do not attempt it. You could really mess up your computer!
Ok, now boot to the floppy. Below is a list of commands you will type, starting with "debug.; The blue is what you'll see on the screen, and the white is what you should type. Be careful to enter each line correctly. Hit <enter> at the end of each line. Good luck!
debug <enter>
- f 200 l1000 0 <enter> * note that's a small "L" before the 1000
- a cs:100 <enter>
248c:0100 mov ax, 301 <enter>
248c:0103 mov bx, 200 <enter>
248c:0106 mov cx, 1 <enter>
248c:0109 mov dx, 80 <enter>
248c:010c int 13 <enter>
248c:010e int 20 <enter>
248c:0110 <enter>
- G <enter>
You should see the message " Program Terminated Normally"
Hit CNTRL/ALT/DEL to reboot
From here, you will want to fdisk to create your partition(s).
Rebbot and format your drives.
That's it! You may want to change to computer's boot sequence so that it doesn't boot to a floppy.
Now load up your operating system(s).
Alternate Method for Blowing Up Your Computer
Gasoline and a match (not recommended)