I am getting this: "One or more files in the Adobe Application Support folder, necessary for running Photoshop, are missing. Please run the Photoshop installer and re-install Photoshop." when I try to run my copy of PS5.5. Er... where do I find the installer? The download does not appear to be available anywhere on the Adobe site.
If you no longer have a access to your Creative Suite 5.5 install files then please follow the steps listed at http://prodesigntools.com/adobe-cs5-5-direct-download-links.html to download Photoshop CS5.1. Please make sure to follow the Very Important Instructions section prior to scrolling down and clicking on the download links.
I would also recommend making a back up of the installation files in case you need them again in the future.