He should have created backups on a regular basis.
You can mount the harddrive in another computer and set it to Slave, copy the info and safely format the hard drive.
I donot think you can solve this problem without formatting, it may have been better not to cancel the progress.
Once you have made backups, you can still try to complete the process to see if it has any effect, if you wish.
Remember, make backups of (important) work on a regular basis.
But how you can confuse a recovery CD for a printer driver CD is beyond my understanding..