Accidentally overwrote boot information on external hard drive.
I was using my brother's computer to make a USB boot drive for Arch Linux. The USB stick didn't show up on his computer and I accidentally wrote the Arch Linux boot information to his 2TB external hard drive (his computer runs windows 7 and it is a WD external hard drive). Obviously, on his computer the drive became completely unrecognized and only asks to be formatted.
When I plug it into my computer and run testdisk it can see the tiny 500mb portion that is assigned to be the boot for ArchLinux and it can see the entire 1.8TB of "unallocated" information still left of my brother's data. Gparted was unable to recover anything from the 1.8TB unallocated partition and it gives me the warning that the drive appears to have GPT signatures but doesn't have a valid fake msdos boot table. When I ran testdisk it warned me that the number of headers and sectors was wrong, but I wasn't able to change them in the geometry section to get it to run right.
I can give you any readouts you need. I'm just not sure what to put up yet. Thanks, I hope this is a good place for this question.