Install operating system?

Further to the previous answer, which is probably correct. When booting, a computer searches for bootable media, this can be an operating system on your hard drive, a setup disk such as the Vista disk in your CD/DVD Drive or a DOS Diskette as mentioned. The order in which the search is conducted is defined in the boot order menu in the bios setup.
You need to enter BIOS setup before the Operating System attempts to load, find the boot order menu and set the CD/DVD Drive as the first boot device.
Entering BIOS Setup is done by pressing certain keys while the system begins to boot, it should tell you which ones on screen, eg "Press to enter BIOS setup", but this is not always the case.
Holding down several random keys during the boot process can sometimes get you access to Bios Setup by causing a keyboard error message.
Alternatively if you are lucky, some systems are set to show which key you need to press to access a one time boot menu which will allow you to choose the CD/DVD Drive as the boot device without having to enter BIOS Setup at all.

www.info-info.co.uk
December 2009

It sounds as though you have not set your PC's BIOS to boot from the CD/DVD drive.

T
December 2009