You do not need to remove the drivers first, but it is probably an OK idea. Unlike what is written above, if Windows does not detect the device on boot-up, it will not load the drivers for it. The same holds true for a USB device for example, or a CD-ROM device, or anything. If windows sees the device exists, it looks for the appropriate driver to load.
Anyway, unloading the drivers before installing your new toy is not going to hurt anything, so its not a bad thing. About the best you will get from it though is the CCC control panel won't start on boot-up.
Now for the fun part! If you have dual PCI-E slots - leave both cards in and have multi monitor fun! I used to have two different video cards in my system in the past to fullfill my need for multiple monitors. In the not to distant past, the only way to have more than one monitor was to have more than one video card in the system.
-S
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