I'd ask "Why?" but the resulting discussion would probably lead to an infraction for breaking Rule 8.

Also, this isn't really a Windows or UNIX question but OS independent.

When booting the Laptop (before even starting the OS), get into the BIOS setup. How depends on the BIOS, but it's usually a key like Del, F1, F10, or F12. Look for something called "Boot order" or "Boot Disk order" and change that to try booting from the CD instead of the HDD. I can't give you exact steps as this depends on your BIOS.

Alternatively, some BIOS' allow for dynamic boot order. On the POST screen look for something called "Boot menu" (or similar), press the associated key & then select your CD/DVD drive. Again, this is dependent on your BIOS.