An "inaccessible boot device" OS message does not necessarily indicate the problem arises as a result of a defective boot drive. While it is entirely possible that's the cause of the problem you're experiencing YOU SHOULD NOT AT THIS TIME RUN OUT TO PURCHASE A NEW DRIVE. You've got to do some more troubleshooting before you reach the conclusion you're dealing with a defective disk.
Since you obviously have a working PC, can you install the "problem" drive in the system internally or as a USB external HDD and then test the drive with the disk's manufacturer's diagnostic program to determine its health? That should be your first step - test the drive with a diagnostic program.