I'm trying to use 4 Monitors with my Optiplex 760 PC. I have three video cards I'm using. I can get the PC to recognize and work with number 1 and 2 so it gives me three monitors but when I install #3 it will lock up when windows splash screen comes up. Anybody have any suggestions on why it's locking up and a work around to get the third card to work? Appreciate the help.
What size power supply do you have on this machine? It may be a power issue.
Which card is the third card you try to hook up? I suspect it may be the second Radeon and since it locks up at the Windows Splash Screen when the drivers are loading, it may be an incompatibility with running two different drivers for Radeons at the same time. You might be able to fix this in the Windows Registry but I couldn't tell you where to begin editing the registry to make it compatible except to start with where the current radeon info is stored.
Getting multiple graphics cards, particularly mulitple vendors and chip version is fraught with problems.
I suggest that you look at a single card solution. Since I see you have been experimenting with low end cards, you are not a gamer and/or are budget constrained?
If so, I suggest that you have a look products made by Matrox. They are well estabilshed in the financial and medical niche for multimonitor solutions. They even have an new product which supports up to 8 monitors!