You should have at least one DVI-I port on your graphics card. You can pick up for cheap (if one wasn't bundled with your video card) a DVI -> VGA adapter and it'll work just fine. DVI-I includes the analogue signal for a VGA monitor. DVI-D is digital only and won't work with a cheap adapter. Lots of cards have one DVI-I and one DVI-D so make sure you plug the adapter into the right port (they look the same, refer the video card manual if it's not labelled on the back of the card).
HDMI or DVI-D to VGA is a pain because you need a digital to analogue converter. They exist but they're expensive and you'd be better off just replacing your monitor.