I have a Desktop PC that is Windows OS and is shared with me, my brother, and nephew. Last night, my nephew logged into my brother's account(to play Minecraft) and when he started it up, from what he told me, he received a pop-up message. He said he didn't remember what the pop-up message said but he pressed something. It rebooted the PC and somehow it wiped half of my brother's desktop account. Some stuff is still there but A LOT of files were missing and were rearranged. He even has the default Windows wallpaper. What's more weird is that when I clicked Google Chrome, it said to "make it into a default browser", when he had it as a default before. It's almost as if he was making his account for the first time. I asked my brother yesterday(he used the PC before my nephew) if it was like this before but he told everything was fine and intact when he used it.

I checked my account and everything on the desktop was there intact except for two things. My wallpaper was just a black screen, and my taskbar color some reason changed into white(it was black before).

I tried to "restore" the whole PC back to how it was yesterday when my brother used it(11/4/20 9:35 AM) by doing the restore point method and started the process at around 1 pm. It's 10 pm currently at my time and all it has been saying "Please wait while your Windows files and settings are being restored. System Restore is restoring the registry..." with the circle animation STILL spinning and with a blue screen in the background.

Could the process be corrupted? I'm not sure what to do. I want to disconnect the plug and restart it but I'm really afraid it would brick my PC or something. What should I do?