Direct3D doesnt work anymore. Why?

I downloaded Project64 about 2 months ago and it worked perfectly with no problems and games did work on it but i uninstalled it becuase i couldnt think of any games i wanted to play on it. I've just reinstalled it and it says "Direct3D failed to initialize. error code 8876086A D3DERR_NOTAVAILABLE." and i haven't changed anything on the computer. please help me

Did you switch computers or something?

What that means is it's incompatible with your graphics hardware or drivers. Try updating the drivers for your graphics card. If that doesn't work you could consider buying an upgrade to your computer from somewhere.