Is it possible to run dual monitors (one as main and the other as an extension, not just a mirror image) on a single DVI port that has a splitter to two VGA ports?
You can't if you are just splitting the image - it will duplicate the display output from DVI. Maybe consider buying an adapter like this if you don't have enough display outputs: http://www.amazon.co.uk/dp/B003NELWWA
Nope. I am pretty sure it will output the same image to both screens.
Which graphics card do you have?
The graphics card is ATI Radeon X600 SE. It is an old card thrown into an old machine at work to try to have a quick fix to postpone purchasing new machines. When the card is installed the mobo on-board graphics is disabled and won't let me re-enable it is why I was going to try the splitter.