|I don't know in depth the signal protocol transferred on the Video Out cable, but I'm sure that what you want to achieve is not possible as|
1- Video Out is aimed to connect the GPU to an analog TV set using the NTSC (USA) or PAL (EU) TVC standard. VGA port is aimed to feed a LCD analog connector in analog way.
2- The signal carried out is analog in nature not digital as in computers (VGA too) and coded to carry video control data.
3- Video Out is GPU (Graphic Processing Unit) not CPU controlled, i.e. it is generated by the video card connected to the motherboard, not by the fundamental chips of the systems.
Why do you look for that is a mystery to me, as today you can connect external backup devices as DVD/CD, flash drives and HDs with a lot of connections: USB, firewire, sata and so on, all specifically planned to transfer massive volumes of data at high speed.