Kemical hasn't mentioned this yet, buy you may want to start thinking about replacing the hard drive. The sooner you take steps to preserve your data the more chance you will have to keep it safe.
If the drive fails completely or is not bootable, you may end up loosing your recovery options and factory image. In that case you would need to go back to Toshiba to get new media or download the Windows 8.1 install media. The Windows 8.1 install media being usable may depend on how the system was originally shipped, and four years ago it was probably Windows 8.
This, of course, assumes the drive is having problems. There could be other causes, such as a virus or some other system problem.