At this point, Curious, I'd say, it can't hurt. You can't exactly break what's already "broken," in a sense.

Whatever computer you're currently on - so you can write down the pathway:

Boot down and do a clean reboot.

Note the changes that have to be made in order to choose the booting direction (from, e.g., C drive to whatever label is assigned to the CD drive on the faulty 'puter).

If you can get the system to boot, you might be able to enter the HD through safe mode.

Too, if you've data that came with the CD, check it out or visit the domain for Mcafee; it may give detailed instructions.