I don't think you formatted your computer's girlfriend, but your girlfriends computer!
And, technically speaking you don't format a computer, you format a partition on a disk. So let's assume you reinstalled the OS doing a format. Which OS? Possible candidates are Windows XP, Windows Vista, Windows 7 or any Linux flavor.
If you install the original OS (the OS that came with the computer) - another thing you forgot to tell) - you best use the original driver. That could be on something like a 'driver and utility' disk or an integral part of the system recovery. But you also didn't tell what source you used to do the reinstall.
So with the information given, all I can say is: keep searching!
I'm French et I'm going to try to speak a good English!
My problem is that I formated the computer's girlfriend, I installed the drivers but I don't find the driver of my video board, even on the website ACER, the driver is not good! The PC is an ACER Aspire 3054!! Impossible to find on the fench forum!!
Thanks for your posts!!