1. Attempt to either restart Windows or open the HP Photoshop Digital Imaging software (whichever brings up the error message).
2. Insert the installation disk into the computer when the error message appears. The disk will have been included when the HP computer was originally purchased.

3. Click 'OK' on the error message window. The installation disk will now run. When asked if you would like to repair or reinstall the software, chose 'Repair.' The installation disk will now scan the system to see what files need to be installed and corrected.
4. Click 'OK' when the repair has finished. The trayapp.msi error should no longer appear.