I've got two 400 GB hard discs on my machine, which have ben almost empty till today - I don't have many big files. Now I have just looked on My Computer, and they are suddenly both almost full! Have I tried to download anything big recently? Not that I can recall - I have tried looking in C drive, but it is hard to find where these big files are. What should I do?
Have you run CCleaner and a malware scan such as Malawarebytes or Superantispyware? If not I would do so.(I assume you have them - all are free). Also how much space have you allocated to restore points ?
Not sure what OS you have, but windows creates "snapshots" of your system - for example when updates are issued. If you have a problem you can restire your system to an earlier time. Do look it up on Google or Microsoft website. Usually you set the amount of soace allocated for this to around 12% of the disc where they are (by default C:).