Hi
Assuming the disk is a rescue disk or a disk provided by MS or the vendor of the computer, it should be bootable.
In that case you will need to go into BIOS and make sure that in the boot order, your CD/DVD player is either the first inline or second only to floppy or other removable drive. I am not familiar with your BIOS as I do not know anything about your machine.
When you go into BIOS, normally by pressing the ‘Delete’ button or maybe ‘F2’ (really depends on you set-up).
You get a blue screen with a black panel at the top with the different sections.
One of them should say ‘Boot’. Navigate there using the arrows and click on ‘Enter’ or on the down arrow.
Somewhere here you should be able to set the order of booting devices.
Come back if you need further assistance.