Hello vjask,
Welcome to the HP Forums! I hope you enjoy your experience here.
I understand your computer can't find the drivers for the Officejet 8600 and 8500. I will do my best to assist you! First, how is these printers connected? Wireless or USB?
I would recommend uninstalling both drivers, since you're receiving this type of error. I will provide steps to help you clean up and reinstall the software on this computer:
Please follow this HP document on Uninstalling the Printer Software from the Control Panel. Next, clean out your Temp folder on your computer by following this document here.
Now, I would like you to perform a clean boot on your computer. Please follow this Microsoft document here to help you. This helps eliminate software conflicts that occur when you install a program, just so this issue doesn't happen again.
You can install the full feature software by using the Printer Install Wizard, which will find the appropriate software for your computer.
Please post your results, as I will be looking forward to hearing from you. Have a great night! :smileyhappy: