Sounds like an incompatibility issue, as VGA is not natively supported on the HD7700.
Have you tried a different VGA > DVI adapter?
Let's start from the start. I wanted to connect my ps3 with my pc monitor so i bought a hdmi to vga converter. I connected the cable i played for some hours and then i i tried to open the pc. After the motherboard loaded the only thing i could see was a black screen. I gave my pc to a pc technician and he also couldnt find what was wrong. Suddendly after a month the technician found a way to fix it. He downloaded some windows drivers and the pc opened. Also he changed the power supply. When i went there to pay for my pc the told me that they lost tha vga to dvi adapter so they gave me a new one. After that my monitor's resolution is awful. The guy told me to download latest drivers for windows and for my graphics card. I did but still nothing happened. Do you think i should change an adapter? Forgot to mention that i tried an other vga cable, still not solved. Thanks in advance.
If the technician had it working, ask for the same adapter.
This is the story with my setup.
Years ago 2 monitors (Primary DVI, secondary HDMI) worked well with Windows 7.
The DVI monitor is 1080p but the HDMI is only 760p. Note I always run Windows in 760p
Upgrade to W10, Crimson 18.104.22.168, the second DPMI monitor not detected. No second PnP monitor in Device manager similar to this problem..
Rebooting, unplugging did nothing. Until deciding to check the HDMI cable by plugging into to the slot of the primary monitor. Unplugged the DVI cable. The desktop window popped up in 1080p, but because we are not running anything like WindowPad couldn't do anything.
Note the HDMI monitor is not capable of 1080p. So reverted to the original config by plugged the HDMI cable back into the second monitor.
Still nothing. About to give up when the second monitor popped up. Yay!
However, the Eyefinity keeps reverting the DVI monitor to 1080p and the only way to change the res back is in Windows.
Fixed the resolution issue by first duplicating the displays, then extending the display to 2. This ensures the second display is always at 760p.
To answer your enquiry, VGA is 640 X 480. Can you get 256 colors to work on it at all?