You can buy a active HDMI-to-VGA converter, something like http://www.amazon.co.uk/HDfury-1080P-HDMI-Converter-Transcoder/dp/B000SOPWS8
( explained here http://www.modsupplier.com/catalog/hdfury-hdmi-to-vga-adapter-cable-p-202.html
As COLGeek said above, HDMI is digital and VGA is analog. Converting digital to analog requires active converters.
On the other hand, DVI can be digital and analog depending on the usage. In your case, you are using the analog part of DVI to connect to VGA.