Hi
I'm having the same exact problem as you. I've spent 4 hours already trying to remove every scrap of the previous version. I removed all references to it in the registry and deleted all the folders and files on my C drive, but I still keep getting that message. I've tried the Download Assistant and I've tried installing Photoshop manually, and I still keep getting the same error message. I also have the yearly subscription but I had to restore my hard drive because of a virus. I was able to reinstall everything else except for Photoshop because of this install error.
Can anyone help us with this problem?!?! PLEASE?