I did nothing but follow the instructions on the Mobility Modder site (any and all credits to Tayrtahn). Just put this link:
http://www.hardwareheaven.com/modtool.php
in the guide for people who have problems updating their ATI laptop drivers, or have updated their drivers but still can't get it to work.
Basically this:
Installation step by step guide
1: Download MSXML 6.0 from Microsoft. (Default in Vista) - Install.
Step 2 is VISTA ONLY
2: Make sure UAC control in Vista is turned off. If you don't know how to do this then read this guide (method 4 is the easiest) or click the "disable UAC" in Mobility Modder.net - please note you MUST reboot after disabling UAC. If you don't want it disabled permanently, you can turn it back on after our mobility tool has finished, but it won't mod the drivers correctly with UAC ON.
3: Download the newest desktop drivers from
http://www.ati.com (or get them from Driver Heaven Downloads). If you are using Windows XP make sure to download .net framework from Microsoft (this is built into Windows Vista so there is no need to install it).
4: Run the downloaded driver, let it extract into c:/ATI/SUPPORT - but cancel the installation once the driver is extracted.
5: Run Mobility Modder - browse to the driver in C:ATI/SUPPORT/ - an example of Catalyst 7.4 would be C:\ATI\SUPPORT\7-4_vista32_dd_ccc_enu_44985 - hit modify. Wait until driver is modified.
6: In Vista, go to C:\ATI\SUPPORT\7-4_vista32_dd_ccc_enu_44985 (Or whatever the driver installation folder was called), and run the SETUP.EXE. Please note you might see a "Driver is not WHQL certified", ignore this, as it is a side effect of the modification.
7: Wait until Install is finished and reboot. Enjoy the new drivers!