So my roommate has been having trouble with her laptop and decided to reformat it. I had just wanted to make sure, but when you reformat your computer, do you need to have the Windows' CD to re-install Windows? I know for Dells they have a special program that allows to reformat it without the hassle of reinstalling Windows and the bundle software. Is there something like this innate to Windows? She has a Toshiba, is it possible that Toshiba has a similar thing (I know nothing about them)?

Also, if I have to reinstall Windows, she does not have her Windows CDs and such, is there any tips as to going about that?