It's because , inexplicably, HP only allow one set of recovery discs to be created from each machine.
I read somewhere about deleting some files to convince it they hadn't already been run off.
Can't recall what it was now , as I never have any intention of buying/relying on a mass market machine.
If I can dig it up - will post back.
In any case, you are better off making your own.
You can do it as often as you like with this great free app: Paragon Backup & Recovery 10 Free Edition