There is currently a free license locking program for the O&O DiskImage 6.8 Professional, you can join to receive the license key by accessing this address and proceeding to fill out the required information.
Check your email for a license key from O&O Software. Then go to this link to download the 6.8 O&O DiskImage version that is suitable for your operating system.
Wish you have a great experience with the O&O DiskImage 6.8.