If you don't mind opening up your system the easiest way is to hook it up as a second drive on the system that does work. Then GDB will work much faster. GDB works best when it is installed on a working system and the drive in question is a second drive.
Also it may be worth waiting to see if Paul Komski happens upon this thread. He is very knowledgeable about these things and it may be a simple matter of undeleting the partition. Again it all depends on what they did to get rid of the OS.
On another note, once you recover your files and if these two systems are identical you should be able to clone your existing drive onto the empty drive and make it work just fine with the other system, if you so desire.
Ultimate Edition Linux
AMD FX 8350
Asus Sabertooth 990FX R2.0
24GB GSkill/Corsair 1866MHz
EVGA GTX 970 SSC/ GTX 650 (PhysX)
SSD - OCZ V4 128GB/Kingston 120GB
HDD - 3TB/2x 750GB/500GB
CM HAF 932 Red
CM Hyper 212 EVO w/2x 120mm Red
Logitech X540 5.1
2X Acer 23" LED - Surround: 3840x1080
Microsoft Sidewinder x4 KB
"The significant problems we face cannot be solved at the same level of thinking we were at when we created them."
- Albert Einstein