1. Remove drivers, when they ask to restart, click restart later
2. Use driver cleaner to clean those left behind files
3. Restart computer, then shut off completely after getting into windows and unplug power cable from psu
4. put in 2nd card and do whatever is necessary for your mobo to enable SLi...ie changing lanes, or SLi jumpers, or whatever it is, you should know it since youve done it already. Dont forget the SLi bridge
5.turn on, install drivers...after it is installed, a quote bubble should pop up saying that you are SLi capable, but dont activate it yet...just restart your computer as requested
6.Then go into nVidia control panel and enable SLi, and make your settings in the control panel, and restart AGAIN...Ive done this many times and it never seems to fail
As far as the whole vga and dvi thing, there have been cases that I've read where some lcd's dvi connection doesnt work well with SLi rigs...mine unfortunately was one of them...sorry im about half asleep right now...anyways, I searched about it and decided to try out my vga cable because i got all these glitches, lines, and color disfigurations thru dvi...and now its perfectly fine. All dvi really gave me was more sharper text, but I wish I could use it...a bit disappointing...it may be my dvi cable quality, but Im happy with what I got right now, vga--->dvi connector is more than acceptable, so im not gonna invest in a $50 monster cable to find out. So try it out, it wouldnt hurt anything.