I mean, if you want it to be default app for opening .lrcat files, then it depends on the OS.
If you mean the app to open when clicking a shortcut, then edit the shortcut.. (which OS?).
Rob-If I have a photo on my desktop and I click on it -I get option to
open in Lightroom. If I click on Lightroom it opens to version 3 instead
of 5.5 the
latest version I have. Just want it to open photo in version 5.
If I have a photo on my desktop and I click on it -I get option to
open in Lightroom.
I've heard of this, but never experienced it. For the post part, Lr opens catalogs not photos - dunno if being registered to open photos was a little mistake or on purpose..
One thing I do know, there was a time when opening a photo with Lightroom would sometimes result in the inability to open Lightroom ever again (without some "hacking"), because it tried to open the photo as a catalog, which made it very confused and unhappy.
My guess is: Adobe no longer supports opening photos with Lightroom (and so Lightroom 5 did not register itself to do that when installed, and so you have an old and now obsolete association), even if at one point it did - but I could be wrong.
Sorry I can't be more help - maybe somebody else will be able to offer more insight and/or a solution.
UPDATE: One thing that might help (if you can't get Lr to open photos how you want) - open catalog instead, then drag those photos into Lr library grid.