Hello, you can always try going into the pre-boot menu, do a disk clear, or partial clean, and flash the latest firmware. I have had this issue before, a handful of times was able to bring the machine back to life doing this process. Keep in mind doing a disk clear erases whatever is on the HDD, so you will need the firmware to install once you have cleared it.
Partial clean, will delete user settings, and will need a firmware install after.
Disk clear, will clear out the HDD, and will need a firmware install after.
If either fail to bring the machine back to life you will need a new HDD.
Hope this helps....