The 4 pins around the flat bit are the analog signal. The clump to the right of that are the digital signal for Link 1, and the gap is where the pins for the digital signal for Link 2 would be if that was a dual-link cable.
The DVI socket in that photo is digital-only, meaning it has no hardware behind it to receive an analog signal.
You'll need to use a DVI-VGA adaptor widget, or get new digital-only DVI cables. Or if you're really sure the computer and monitor both support digital-only, break the analog pins off the cable.
Ahh, I gets you. Of course, the other question is why on earth you're still buying (in 2011) monitors with only VGA ports. All the ones I've bought for the last 5 years or more have had both VGA and DVI ports on them - and that includes the cheap ones at work!
Still, looks like your only options are to replace some of the monitors with DVI supporting screens, or buy some graphics cards which support dual analogue outputs.