I have a toshiba satellite c855-s5115 that was given to me because it is either missing windows or hard drive has failed. The computer reads that the hard drive is present in bios but has the checking media failed no bootable disk error. I have tried resetting it to factory but when i click the restore button it just goes to a gray screen with black dots on it and didnt do anything else after that. Am i doing something wrong or is it the hard drive itself that needs replaced