and put it back the way it was.
You have "on the motherboard" video, not a specific card. If you had NO video . . .
Investigate the on board video in Device Manager. Look for updates. If there are none then a separate video card is needed.
I got a userd computer for my kids. Turned it on and the display was 640x480 - not even sure I have a vid card. I messed with the settings and got it to 1024 (it was much more difficult than it should have been) but it was only 16 bit color.
Messed it with more, rebooted, now there is NOTHING on the screen. No cursor, nothing.
What can I do?