I'm using Win7 64bits on an AMD E-450 with 8 GB of RAM (Zotac AD04)
GPU acceleration worked ok on 12.3.
Also notice that 12.6/12.7 GPU acceleration works ok on MPC-HC and flash.
It seems that 12.6/12.7 break GPU acceleration ONLY on VLC

I'm just informing about the problem. No need to tell me to go back to 12.3.