If you're on a Mac, Adobe installed an Uninstaller on your HD when you installed CS4. Use that, then install from the original media.
For next time:
If you give complete and detailed information about your setup and the issue at hand, such as your platform (Mac or Win), exact versions of your OS, of Photoshop and of Bridge, machine specs, such as total installed RAM, scratch file HDs, video card specs, what troubleshooting steps you have taken so far, what error message(s) you receive, if having issues opening raw files also the exact camera make and model that generated them, etc., someone may be able to help you.
Please read this FAQ for advice on how to ask your questions correctly for quicker and better answers:
If you are on a PC then you can uninstall one of two ways
1) add / remove programs
Go to Start --> control panel , now change the view to large icons, now near the top you should see "add / remove programs selct it
in the list find Adobe Photoshop cc and click change/remove. this should start the setup program and give you options to remove it from the system.
firstly find Photoshop on your desktop right click and select properties, in the window select "find target". This will open a window showing you the location where photoshop is installed. within this folder find "uninstall.exe" this will start the same process and you should be able to follow the steps to remove.
Hope this helps , otherwise here is a step by step guide with pictures How to Guide: Uninstall Adobe Photoshop CS4 - Tee Support Blog