I wanted to know how can reboot my computer without using the disc?

Do you have access to the setup screen?
You may have to push DEL many times while you start your computer-go to advanced setup screen and check boot priority, select the required boot device-usually a CDROM nowadays or a DVD, (provided you have a bootable disk), then it should boot up without your hard disk. A better way is to have a rescue disk for your computer which usually has windows XP or vista on it which will boot the computer for you.

I wanted to know how can reboot my computer without using the disc

Do you mean reinstall windows with disc?

I want reboot my comuputer and also want to save the files and folder. How I will rebout it please guide me?