I have a Dell laptop with C: 58Gbytes and D: 392Gbytes
My C: is continually full and despite transferring various folders from C to D - it still continues to fill up leaving me unable to update McAfee etc - current usage
C: shows 53K from 58G free - D: 392G from 397G Help!!
It would also help to see what is using the disk space by using something like WinDirStat or TreeSize (both free.) Restore points, backups or system images, large temp files generated by video/photo editing programs, even malware could be contributing to the loss of disk space.
Finally, it would also help if you could provide your system specs. At the top of any Forum page click on "User CP" and then in the left column that opens click on "Edit System Spec". fill in as much as you can.