I had some trouble with a PC that kept rebooting itself in a continuous loop. Through Windows Recovery Console I used fixmbr, but after restarting I received the message, "Invalid Partition Table". Now I cannot boot from the disk at all nor can I read from it when connecting it to other computers using a SATA/USB cable.

What can I do to get data off of this hard drive?

After the MBR fix was applied were you still getting those beeps while booting?

What model drive is this?

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Hard Disk Drive (HDD), Solid State Drive (SSD, SATA, NVMe, etc), USB Flash Drive and RAID Data Recovery Specialist in Massachusetts

I was not getting beeps at all. Just the message, "Invalid Partition Table," which did not appear until after I used fixmbr.

The drive is an 80GB Western Digital (WD800JD).

You said "nor can I read from it when connecting it to other computers using a SATA/USB cable."

Did the drive register in Device Manager when you connected to other computers via SATA or USB?

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Hard Disk Drive (HDD), Solid State Drive (SSD, SATA, NVMe, etc), USB Flash Drive and RAID Data Recovery Specialist in Massachusetts

Plug the drive into another computer and run testdisk to read the drive. If testdisk finds a partition, you may write this to the drive, then reboot to see if the files are accessible.

Knoppix live USB has test disk, or you can burn the Testdisk ISO to a cd/dvd and boot from that.