Mon May 14, 2012 12:11 pm
I think I see where you're coming from...
The Raspberry Pi is a USB Host device, not a Slave. This means it can control/use other devices connected via USB, but it cannot be controlled by a USB connection. The microUSB port is for power only; it doesn't work the same way as it does on, for example, a smartphone.
Are you sure your display does not accept analogue signals through the DVI port? If it does then VGA to DVI adapters are quite cheap. Your laptop will still only be outputting an analogue VGA signal - a simple converter won't magically change it into a digital signal - but if the display accepts this then there's no problem.
If your display doesn't support analogue signals at all then I'm afraid you may be out of luck. As you've already discovered, converting VGA to DVI-D (digital) is not a cheap prospect. It's probably cheaper to pick up a spare VGA display...
. I'm currently searching for cheapest possible solution how to connect my VGA notebook to DVI display. Since 'standard' conversion via external adapter USB3->DVI/HDMI is expensive as hell 
(50$+), I thought it might be suitable to use Raspberry PI as USB->DVI adapter. I have no idea if it's possible, so I would like to ask you for your opinions. 