Subsequently, control panel became corrupted (at least it would not launch), so I repaired/reinstalled win xp (which was SP2 at the time). I have not applied any service packs yet, so am currently at a '2600 build'. Control panel works fine at least. Computer does not recognize any display adapter, and appears to be in some sort of "VgaSafe" mode.
I have attempted to reinstall the old Geforce card, but ITS installation wizard fails as well. So I started all over again, removed in control panel all drivers. Attempted to reinstall the Radeon--wizard still aborts.
So I applied Driver Cleaner, against both Nvidia and ATI drivers. Ran the included "Cab Cleaner". Did this in Safe Mode, per instructions. Attempted to install Radeon card (which I would even remove from AGP slot, and reinstall), did this several times, each time I get the same ATI wizard abort.
Any advice at this time would be much appreciated. What more can I do? Does ATI have tech support, and might THEY know if I have am missing something completely trivial, or obscure for that matter? Thanks for any and all help.