Thanks to MerlinUK on AMD Game Forums, I have managed to get the video card driver to work on Win7. You can find the original post here.

If you are running x86,

1. Download Catalyst 9.3
2. Extract Catalyst and browse to X:\ATI\Support\9_3_vista32_win7_32_dd_ccc_wdm_enu\pakages\drivers\display\LH_INF
3. find

[Manufacturer]
%ATI% = ATI.Mfg, NTx86.6.0, NTx86.6.1

and change it too

[Manufacturer]
%ATI% = ATI.Mfg, NTx86.6.0


4. Now manually install this modified .inf from Device Manager, ignore the warning
5. Enjoy Win7 with correct resolution, though there’s no transparent effect for me, but at least it’s better than the distorted 4:3 display

found a better solution, just go to this website and download Catalyst Version 8.12, extract the installer and manually install the driver in device manager, everything works, including aero!