Unsatisfactory laptop repair Dell Inspiron 7720

Laptop: Dell Inspiron 7720 Turbo/Sepcial Edition 3D

Core i7 3610 CPU (2.3-3.3 GHz) | 8 GB DDR3 1600 MHz RAM | 1TB 5400 rpm HDD + 32GB mSATA SSD | nVidia GT 650M (3D) graphics

About 2 months ago, the GPU of my laptop fried, along with HDD crash and other battery problems. Since I wasn't in India that time, I sent the laptop back there and asked Dell for help. A serviceman was sent to my home (I wasn't there personally to see the repairs), and I talked to him on phone about the condition of laptop.

He replaced the motheboard, Battery, Touchpad and Hard Disk. Then he installed windows and went away. Since then, no one operated the laptop till i came home yesterday. And here's what I found:

• Only Windows was installed (no drivers)
• nVidia Graphics was not detected
• There was no way to test if 3D display was working
• There was additional 29GB drive of mSATA SSD in My Computer (no Intel Rapid Storage)
• BIOS version was A13
• BIOS Settings under SATA mode showed no Intel Rapid Storage/ Smart Response. Only ATA and AHCI
• The SATA mode was set to AHCI
• No Settings to turn off USB powershare
• Service Tag from BIOS was gone

So here's what I did to try to get my graphics and everything back:

I downloaded the new A15 BIOS to detect nVidia graphics, but it failed to install from Windows 7 interface. So I flashed BIOS using bootable-USB method.

After BIOS upgrade, the system failed to boot - Showed error:

Operation System not found

I looked into the BIOS and the SATA mode was set to RAID. I changed it to AHCI as it was before and rebooted, but it showed same error again.

Also, there was lot of other new options available in BIOS which were never seen before under Hard Disk management.

I put in Windows 7 Reinstall DVD that came with laptop and booted. It took unusually long to run Windows Install Setup. But even then I could not install windows on my 1TB HDD. It gave the error:

Windows cannot be installed on this partition. The selected disk is of GPT partition style.

So I tried formatting the drive, but error was still the same. I deleted the partition from there, and tried to create new, but failed. It simply wouldn't create a new partiton from 931GB unallocated space.

I tried using the 29GB mSATA SSD to install windows but even there it showed error (GPT partition style)

Now, there is no way I can boot windows, or install windows anywhere on the laptop. And the BIOS is all changed. Plus I'm not even sure if the replacement motherboard had the NVidia GPU on it or not.

Please help.