Go to the Windows Control Panel >> Programs >> Programs & Features
If both applications are installed you should see Adobe Lightroom and Adobe Photoshop Lightroom 4.4
Highlight Adobe Lightroom and click uninstall.
Thank you Jon. I don't want to delete lightroom though. Are you suggesting that to reinstall will solve the problem?
Will I lose all the catologues, collections and presets I have in there? I'm currently working on 5 galleries and don't want to have to cull again if I don't need to?
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Uninstalling or re-installing won't affect your catalog. I'm only suggesting you uninstall Adobe Lightroom which will be the CC version you don't need. I should have said to uninstall Photoshop CC but am assuming you may have also been using LR CC. If so uninstall both CC versions of LR & Photoshop.
For Photoshop uninstall Adobe Photoshop CC 2015
Also try re-booting your PC and relaunching LR so that it recognizes CS3 as the only installed version of Photoshop.
N.B if you have created collections or done editing in LR CC that work won't be backward compatible with earlier versions.
After un-installing LR & PS CC versions-
If the above suggestions have not worked for you, I would suggest the Solution in the link below-
It involves editing the registry, so if you are not confident doing this, can you invite a geek friend to follow the directions.
Solution 2: Re-create the Photoshop.exe application path registry key.