My daughter has been using my copy of CS4 for over a year without issues. Recently however she began to have some kind of issue with the brushes pixelating. We deactivated (just to be safe) and uninstalled then reinstalled. That fixed the problem. For a short time. When the issue returned we again deactivated, but this time it somehow did a complete uninstall which included the original setup program maybe? So, we downloaded PS again but we can only find a way to download PS CC. Now when we go to put the serial number in, it won't accept it. Is there someplace we should be downloading CS4 specifically? I never got disks...only a digital download years ago. Suggestions?
A piece of advice first. An uninstall rarely is necessary to solve problems. You just need to reset preferences by holding down specific keys.
How did you install the first time without disks? Another word of advice on downloaded programs. Burn the setup files to disk for future use.
You may have a mess now if you have various versions downloaded. Uninstall them and download CS4 from http://prodesigntools.com/how-to-get-prior-adobe-software-versions-cs4-cs5.html
Be sure to follow download instructions exactly or you will run into problems.