I have both 4.0 and 3.6.5 versions of the software, but neither want to open. They just crash the moment I click on them.
So… any more info…?? You know… some people try to install blender on android… or don’t know why it isn’t running anymore on their Window XP ( ← no … this is not a typo…)…
Since i did a very quick look into your activities… you seems to have run at least some older versions… ??
Try to download it from Steam (if you have one) and run it from there.
I usually update when the newest version comes out. I had to get 3.6 again when I found out not all of the addons compatible with that version worked with 4.0.
OS currently is Windows 11 and I’m using my Desktop for the software. I was trying to install a rigging addon when the software just crashed and neither version would open. I did a reboot and it works now, but I don’t want a repeat of what happened last time, so now I’m wondering if there’s a way to prevent it from happening again.
@goorman I actually get my copies from the official Blender homepage, not Steam.
Sometimes…
…it’s just… computer gremlins…
Go to %appdata%\Blender Foundation\Blender (that’s where your user preferences are stored) and rename or move the folder for the version you are trying to start to see if your user preferences are the problem. User installed add-ons are in %appdata%\Blender Foundation\Blender\4.0\scripts\addons so if the add-on you installed is causing this, deleting its script or folder from there will fix it. GPU drivers are another most common cause for Blender to not work properly and even if you haven’t updated them manually they might be updated by the OS automatically. If there is a bug in a new driver it might also cause trouble. Updating it again manually or installing previous version might help. I think a broken add-on is more likely.
Also make sure your PC meets minimum hardware requirements. If not, the solution is very easy - just buy a new computer. 
But if it came with WIndows 11, that’s probably not the case.