Unity 2017.3 wont recognize a fle

I used to have Unity 4.2 I recently downloaded unity 2017.3

I worked on a project in unity 2017.3 for a few hours over a few days. (Saving before closing each time, and then successfully opening at least twice.)

Yesterday, I went to open the scene file directly from my files, and it opened in the older version of unity, except instead of opening the file I clicked, it opened a file I had been working on in the older version.

I tried to open unity 2017.3 and open the file from that application, but it wasn't in the list of projects I had already worked on. (although I'd already openned it in unity 2017.3) The file was clearly in the folder labelled repos, but it also wasn't showing up when I attempted to locate it through the unity 2017.3 "open project" function.)

So I completely uninstalled unity 4.2. Tried to reopen the scene file, to which it said the file had no recognised apps it could open in, so I browsed for unity 2017.3 in file explorer and attempted to open it. Instead of openning the project in unity 2017.3, it simply openned up the start wizard for unity 2017.3, no project.

Could someone help me understand what's going on? I would like to be able to open this project in unity 2017.3, but it seems that the pc gods have decided it is not my time. I have a feeling that the problem might have had a connection to the fact that I'd initially somehow let both versions of the application simply have the name "unity". I thought I attempted to avoid this but I guess not.

Thank you to anyone who can help!! :)