I would say that the AMD driver page for the HD4xxx card (Win7 x64) is INCORRECT.
It shows that 13.1 is the current driver, but the English description is still what it was for the past 7 months or so ever since 12.6 Legacy WHQL drivers became the LAST drivers usable for thd HD4xxx cards and below.
I have an HD4850 on my machine, and have 12.6 drivers currently installed. I just tried to do an install of the 13.1 driver package (which I have for my other other machine, which has an HD5770 in it, which DOES use newest drivers) and the custom install which showed me what was available for installation (i.e. what was not already currently installed on my system) were two sub-features I always un-check and don't install.
But (a) AMD Display Driver 8.970.100.3000 is already installed, and is apparently THE MOST CURRENT VERSION USABLE because no newer version from 13.1 is in a check-box, and (b) Catalyst Control Center 2012.0704.122.388 is already installed, and again is apparently THE MOST CURRENT VERSION USABLE because no newer version from 13.1 is in a check box.
I believe
this AMD driver page is where you click to get that latest 12.6 Legacy WHQL driver for the HD4850.
But you DO need to first remove your existing v11 Catalyst drivers and CCC completely, before installing this new 12.6.
In my own experience, the removal of ATI drivers using ATI's install manager is never (or not reliably 100%) completely successful. I previously used
Driver Sweeper to remove everything before installing a new driver release, but the product has been re-branded as Driver Fusion by the software vendor and it's no longer free if you want the "premium features". There is a stripped down free version which could be adequate, but I bought the "premium" version to get everything and also support the software vendor.
I don't believe the original Driver Sweeper (free) is being maintained any longer, so it's probably a bit out of date although it could probably still work just fine. But I myself am now using
Driver Fusion which is the currently active product from the software vendor Treexy.