Microsoft Windows is very stable now. No need to format Windows when system crashed. I still remember the day when using Microsoft Windows 95 / ME. Windows is not so stable and tends to crash if the applications do not running well. Boot disk is a must have to troubleshoot. I was using floppy drive and CD ROM as boot disk back then. But it is replaced by USB flash drive nowadays. How to make USB Pen Drive bootable? There is a tool called Makebootable from PenDrive that can make your Pen Drive bootable.