Then don't delete it.
A few weeks after I installed Prepar3d V3, I deleted V2.5 from my SSD. Didn't need it.
Or did I.
After clearing a large amount of space off my SSD C: drive, and starting to set up P3d V3 the way that I wanted it, I had to stop and think a moment. Or two. Or three.
See, I had re-installed FSX and was thinking that even some free programs will only install to the FSX directory.
For instance, the CoolPlane.exe (fictitious) program may only install to the FSX directory. But from there I can copy it to Prepar3ed V3 where it'll be a wonderful plane to fly.
Welllll........... The same thing is true about Prepar3d V2.X programs too. And while I had copied my scenery, Effects, gauges, and SimObjects to another drive, that alone might not be good enough.
Not a problem. I burn the programs that I buy to DVD along with whatever email and ID/Password that I might need to reinstall it.
BTW -You can't use the Setup.exe program. You have to use the Prepar3D.msi installer to get the program on your hard disk if you've already installed P3d V3.
So I install P3d V2 again, run it, and entered the required ID/Password - NOT ACCEPTED.
I copy & paste everything, just as I do when installing it the first time. NOT ACCEPTED.
NOT ACCEPTED.
NOT ACCEPTED.
So while you CAN have both versions running on one computer, you can't, apparently, RE-install the older version.
However, I don't really want to "fly" anything, anywhere. I just want it there for install purposes.
And for that, it works perfectly.
I'm somewhat sure (maybe) that if you really do need it to work, LM will let you do it in some way. Probably.
Just don't forget to