Hi, I searched every where and I had your problem too. I previously used 10-02_legacy_xp32-64_dd_ccc and mobility modder to install the Radeon x300 on windows 7 but they don't work (in any way you try) in windows 8.
Here what worked:
1-Get the zipped copy of 10-02_legacy_vista32-64_dd_ccc and copy the unzip folder to
C: ATI, and
C:Program files: ATI, but DON'T INSTALL anything.
2-Right click on the scree, select screen resolution, monitor, advance options, update drive, select folder, have a disk, and then browse the c:program files, ATI folder and let the windows install it. Ignore windows complaint about the drive and install it anyway.
You should have it working without even a reboot.