How do I find what is taking up space on a hard drive? Last summer I built my mother a computer(windows 7), however now her smaller SSD for the OS is filled up. She's been good about not saving to C: and I couldn't find anything there that she saved. I tried appdata, but when the file was trying to move it showed up as just a few MB. Is there any other large storage occupiers that I could clear or move? What is filling it up?