I just downloaded the 9.9 Catalyst for Win 7, x86. I only have 9.10 beta available on my machine at the moment. I'm going to have a look and post the custom .inf for you in a few moments.
Edit: Here ya go. Directly overwrite your exisiting .inf in C:\ATI\Support\9-9_vista32_win7_32_dd_ccc_wdm_enu\Driver
\Display\W7_INF with this one. Then install manually from the device manager, specifying this file. Update driver | browse my computer | let me pick | have disk | browse. http://***************/files/294766516/CL_87738.inf.html
Reboot after may be necessary. Choose an Aero theme after, if the UI appears basic after reboot.
All 3850 AGP have dev_9515. Check that yours is too, because that's what the .inf was made for. It's a good idea to winrar the entire contents of C:\ATI to a .rar file so you can save this for any future installs. Or for new Catalyst versions in the future, you can still use this .inf in all likelihood.