When you upgrade from Win7 (or any other version) to Windows 8, you have to fully remove the old Catalyst software first. The drivers are completely different, but Win8 will try to apply those drivers and files anyways, since most applications that it converts aren't OS-specific. If you do a complete uninstall of the Win7 software and install the Win8 software, you should be good to go.
You're also using the 12.6 Win7 Legacy installation suite (no Win8 drivers inside), which won't help at all. For version 12.6, use http://www2.ati.com/drivers/legacy/amd_catalyst_12.6_legacy_win8.exe and for version 13.1, use http://www2.ati.com/drivers/legacy/13-1-legacy_vista_win7_win8_64_dd_ccc.exe .
I know it's a little late, but if anyone else has an issue with it, they might find this useful.
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