Weird Science

I am pretty sure my computer has a mind of its own entirely. Everything will be fine and normal with it and then I will leave it for a matter of hours. When I return, something will be changed. For instance, lately the size of fonts on the screen have been altering themselves. Not just the fonts, but everything. Including the size of the icons and such. I know that has a name and a way to change it, but I don't remember the name now and I don't know how to fix it without searching for a while. Kelly said he doesn't know how to switch it at all, so I know it isn't him. Also, sometimes I'll leave windows open at the bottom of the screen but when I come back they're closed. Sometimes my wallpaper will be gone and I'm left with a blank dark green screen. I also know it isn't Kelly because whenever he uses the computer, he turns the volume up as high as it goes. That hasn't happened for some time. Basically I have no explanation for the behaviors my computer exhibits.