Hi,
If you are positive you have the correct HP recovery disks and they do not work because of viral corruption, you could try wiping the drive with this program. Then try HP recovery disks again.
Will HP restore the operating system at no charge? If not, it may be cheaper to purchase a new drive of similar size. Install the drive and try the HP recovery disks on the new drive, if wiping the installed drive fails. Is the HDD accessible? I have never worked on an All in One system.
HP tatoos the mainboard which ties the OS installed at the factory to the system board. Hard drives can be added to the system with no issues.
Jaco