i believe as your Hardware is working perfect as you said, then it might be some Bios misconfiguration,
probably your bios is configured to boot from Hard Disk drive first then CDROM next, in that case the Bios when you turn on your laptop will first try to load any loadable Bootloader (Operating system) if it fails (system not found, or the Hardware is not working or some other reason) it will move to the next one CDROM.
that being said about your issue (and hopefully it's what you've encountered); you can easily fix it using one of the two methods below:
Either at startup push the F8 button so that you can access your Bios configuration, and look for Boot Devices Order, and reorder your devices so that your PC will start from CDROM first then Hard Disk drive next.
Or you can only Press the F10 Button at startup, that will show the "Select the Boot device" Screen you can select to Boot from CDROM.
The difference between the two methods is: the first one will save that configuration, so every time you turn on your machine the bios will try to start with CDROM first. while second method will only do that once, so whenever you need to boot from CDROM you'll have to press that F10 button again.
"If i were you i would suggest the second method as you need to format your machine only once "