if you got a 3.5, you can find boot disk from www.bootdisk.com for windows, dos and linux. There are some other sites and if you dont have a 3.5, google for dos boot cd
Then that shouldn't be too hard, just pop a floppy disk into the drive, and then right click on the A:\ drive icon and select format. A dialog box should come up and then there will be an option to turn it into a start up disk.