HDMI inputs on monitor's are usually for using DVD/BD players. They use the TV standard hence you get issues like having to correct overscan, as well the resolution is LOCKED so you can't change it in a game.
What you want is this:
1) DVI->VGA adapter for your graphics card
2) VGA cable
How it works:
Your graphics card is sending BOTH the digital (DVI) and analog (VGA) signals to the DVI output. The VGA adapter is simply connecting to ONLY the VGA signals.
See your motherboard manual because some DVI outputs are "DVI-D" meaning just the digital so no VGA adapter works and some are "DVI-I" meaning "integrated" (it has both outputs).
DVI->VGA adapter (should have come with graphics card).