I used to install Cable Modems. This was back in the windows 98/ME days. Over HALF the customers I handled had no earthly idea where their install CDs were. A hard drive partition install is a good idea. Can't misplace that. Its right there. Problem 1 is: The "computer guy" deleting the partition. Problem 2 is a hard drive crash.
CDs are too easily scratched. Many of the customers who DID have their install CDs, had them stored improperly. They were unusable. If they were usable the customer didn't have a clue where the CD key was.
I don't blame the companies for going the partition route. 75% of the time the person will lose it. A partitioned copy is much harder to lose or destroy. Besides, if you aren't going to take the initiative to protect your investment then you get what you deserve.
Get Wintoflash and a 4 gig USB flash drive. It only takes a few minutes to make a bootable windows installation flash drive. Its much harder to destroy that copy.