You can make the 8.3 setup work if you edit the files...
run the install
go to C:\ATI\support\8-3_xp32_dd_ccc_wdm_enu_59746\Driver\Driver\

CX_59746.INI
,0x9505:0x30001002,
to
,0x9505:0x30001002,0x9515:0x00281787,

INSTALL.INI
,0x9505:0x25421002,
to
,0x9505:0x25421002,0x9515:0x00281787,

Driver.Dat
,9505,
to
,9505,9515,

go to C:\ATI\support\8-3_xp32_dd_ccc_wdm_enu_59746\Driver\Driver\XP_INF

CX_59746.inf
find "ATI Radeon HD 3850" and add...
"ATI Radeon HD 3850 AGP" = ati2mtag_RV630, PCI\VEN_1002&DEV_9515&SUBSYS_00281787

run C:\Drivers\8-3_xp32_dd_ccc_wdm_enu_59746\Driver\Setup.exe


8.3 contains 14 other files that have a reference to 9515
8.2 contained 13 other files that have a reference to 9515
extra one is
C:\ATI\support\8-3_xp32_dd_ccc_wdm_enu_59746\Driver\BIN\chipset.msi