After trial-and-error and reading numerous articles and posts on this website and others I thought I would pass on IMHO what I know.
Always write down original settings in BIOS before altering and create a
restore point/backup registry.
NOT ALL BIOS HAVE THESE SETTINGS.
In CMOS:
1)enable 4x(8x) AGP
2)disable Fast-Writes(unless you have Radeon 8500 series or higher)
3)disable all Video and BIOS Cachables
4)disable Video Shadow(ATI cards do this auto.)
5)set AGP Aperture to one half of available RAM or max.
(ie 512mb x.5=256)
6)enable 4 way memory interleave

Reboot

7)if you have ATI MMC installed remove it and go to regedit and
delete any ATI files(HKEY_CURRENT_USER & HKEY_LOCAL_MACHINE>SOFTWARE)
8)run scandisk and a Utility such as Norton Windoctor.

Shutdown

Install Videocard and boot up

9)install video drivers and reboot
10)install ATI Control Panel and reboot
11)install MMC and reboot
12)go to Explorer and delete any ATI folders NOT located in Program folder,if you don't see any don't worry.
13)run scandisc and Norton Windoctor.

To get excellent captures set color to 32BPP,resolution to 800x600 and refresh rate to 60hz.In ATI Control Panel set all sliders to Quality.

Hope this guide helped.