Go to the HOW TO & FAQs forum, I've posted up some solutions to this common problem a zillion times now and it features in that sub-forum .. handy things these free forum search engines, amazing what you can find if you use them ...
12.6 Legacy drivers can cause issues ( I had a few myself whilst testing them ), so if older drivers work and you're not having issues as described in the release notes, then you really don't have to update, you won't be missing out on any chocolate milk & cookies ..
I have also posted up in the Extended Support forum, a link to a modded version of the 12.6 drivers which work just fine ( assuming no o/s glitches, .NET errors etc already present on the system being updated ) ..
Oh, and all you really had to do, was to swap the cable over from VGA D-Sub to DVI, plug it into the DVI port and it'd have worked straight away with a DVI signal .. you don't need to update drivers just for swapping a cable over ..
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