Because I has dedicated vram of 1gb so I felt that I don't need to share my system memory from windows? It's only 4gb. I disabled memory remap feature in BIOS <- what's that for?
Prob not a good idea to play with BIOS settings until you know what they do. Shared memory is the amount of system memory DX can allocated for GPU data if necessary. VRAM + Shared = total video memory = half system memory. Remapping is something different altogether and should always be enabled.