The suffix letter after DVI indicates what signals the DVI carries. DVI-D only has digital pins, DVI-A (which doesn't really exist) would have only analogue pins, DVI-I has both digital and analogue pins. VGA is an analogue signal, so you can't use a VGA monitor without a video output with VGA-type analogue out. Only DVI-I has the analogue signal compatible with VGA.
There are converter boxes, but you'll probably be best using a better monitor...