I have a Radeon HD 5850 (Asus) installed running on Windows 7 64 bit.
I've been using the 11.12 drivers for a while, and decided to upgrade to the latest - 12.04. I duly un-installed everything 'catalyst' related on my PC, finishing with a Drive Sweep in Safe Mode.
I then installed the 12.04 package (12-4_vista_win7_64_dd_ccc.exe).
After rebooted, Catalyst Control Centre reports the version as 11.12 (look under Information -> Software)
I've been through this process several times, but with the same result. Am I being amazingly thick here, and missed something, or....what? Is the number just incorrectly reported?