My son's laptop had some issues so Minecraft isn't working properly. If we delete all the Minecraft files and reload them, will he lose everything he's acquired in the game? He has a paid version. What about Pixelmon that he plays in Minecraft? Will he lose everything in Pixelmon as well?
Deleting minecraft files?
I'm not sure about Pixelmon, but I may be able to help with Minecraft files. First, make sure your everything on your computer is updated; java, minecraft, etc. If everything appears to be in order, go to the start menu and type "run". Click the program that appears, and type "%appdata%". A folder should appear called "roaming"; open it up, and click ".minecraft". This is the minecraft folder; because it is a hidden folder, you can't access it unless you are using run. Once you are in the minecraft folder, click "saves". Now, copy and paste his worlds to the desktop and get them onto a flash drive, just in case something goes wrong while you are trying to fix the game; this way, he won't lose all of them. Now you can delete his worlds from minecraft directly, and then try copying and pasting all of his saves from the flashdrive back into the "saves" folder. This will just reload his saves, I don't know if it will actually fix the problem though. If it doesn't, try loading the worlds on a different computer by copying and pasting them from the flashdrive to the "saves" folder in the minecraft folder on that computer. If they don't work on another computer, then the worlds are probably corrupted, in which case there's nothing you can do…
Alright here is what you do. Press and hold the windows key and then press "R". Now you have "run" opened up. Type in "%appdata% " there's going to be a file called "roaming" inside that file there should be a folder called ".Minecraft" click on it once and delete it. Now Minecraft is completely deleted from your sons computer. Now go to https://www.java.com/.../download/ to install the latest java update because Minecraft runs off of java and without it you can't play Minecraft. Now once you have the latest version installed, i want you to go to https://minecraft.net/...craft.net/ and (Re-dowbload) Minecraft. Once Minecraft is installed run it and log in. I hoped this helped you, i'm pretty confident it did, all of your issues should be fixed.