I bought a new computer monitor (a Dell) and the VGA to minidisplay converter wouldn't allow me to split the screen, so I purchased a VGA to DVI cable and then a new minidisplay to DVI adapter. It is working on my MacBook Pro (I can drag windows off the side of the screen, presumably onto the second screen I am trying to hook up) but not on the Dell computer monitor. Nothing shows up and it says there is no signal coming from my computer. Any idea why or how to fix? Please and thanks.