Ultrabook HP ENVY 6-1100sl Win8 x64 - Vga not detected and AMD drivers not working

So... This is the problem that's been harrassing me in the last two days.

While playing a game my laptop crashed and it wasn't able to boot windows 8 anymore, restore point didn't work, boot fix didn't work, complete hp restore didn't work. So I brought the pc to a tech (I wish I didn't have to do that, but I didn't have enough time to try and fix it myself...) and he made a clean win 8 installation (all the restore methods were broken), with a quite poor excuse of reinstalling "all" drivers too, but then I noticed that the amd drivers for the hd 7670m were missing and that the card itself wasn't detected by the device manager, only the Intel one is listed.
I've tried to install the last drivers from hp, but they won't install at all (Installation Failed: Install Package Failure), moved to the official up to date drivers from amd, same error, I've even tried the modded ones from leshcat, same error.
Tried a clean drivers install after wiping the ones installed by the tech with driver fusion in safe mode, but nothing worked, it refuse to install amd driver and the graphic card is still not detected. All of this, I've tried doing it more than once.

So, long story short: all is up to date, bios and chipset too, the hd 7670m is not detected by device manager, any attempt to install amd drivers (using the ones from hp, from amd and from leshcat) lead to a "Installation Failed: Install Package Failure!".

Any ideas? May the vga be dead?