Dan Marchant wrote in post #18987560
You say "(re)installed". By that do you mean it had been uninstalled and that you were now doing a clean (re)install? If so, and auto update is de-selected, then the option to delete an earlier version wouldn't apply (and so would be greyed out) for two reasons....
1. There is currently no earlier version on your system to remove, and
2. The system won't automatically update to a new version so it does not need you to select your preference for delete/keep the old version - that option will be presented to you each time you choose to manually update (as per the screen shot above).
It was rather weird. I already had PS CC installed and had been using it for a year or so then, when I read this thread, I thought I would check to make sure only one version was installed. When I checked as per the instruction in here, Adobe said PS wasn't installed at all ... Eh?
Anyway, I went along with it and 'installed it' again, though Adobe CC still seems to think it was never there. I only have one copy installed now, called 'Adobe Photoshop 2020' whereas I think it used to be labelled simply 'Photoshop'.
Oh and, instead of making PS run faster, as I hoped, it now seems even slower than before 
5D3, 7D2, EF 16-35 f/2.8L, EF 24-70 f/2.8L II, EF 24-105 f/4L, EF 70-200 f/2.8L II, EF 100-400 f/4.5-5.6L II, EF 1.4x III, Sigma 150mm macro, Lumix LX100 plus a cupboard full of bags, tripods, flashes & stuff.