What edition of Windows do you have? (7/8/8.1?)
Right click C: drive in Explorer > Properties > Tools > Check for errors (select both checkboxes)
It will likely ask to restart and may take a while.
There may also be some hidden partitions
Press Win key+R and type Diskmgmt.msc
Right click first hidden partition and Change letter. Call it P:, say.
Repeat for any others, eg Q:, R:, S:
Back in Explorer, you can now right-click those drives > Properties > Tools etc and check for errors. They won't take long.
You can remove the drive letters when done.
Or it could me a Memory module problem or a Power Supply problem, but they may be tricky on an All-in-One PC.
If you can get at the modules, try re-seating them, or swapping them over.