I have a Chaintech ZNF3-250 mobo with an Nvidia Geforce 5500 (right now). However, I'm planning on getting either an X800 XT or 6800 Ultra. Personally, I like the X800 better because it uses less power. I was wondering if it would work on my mobo.
You just have to make sure that you completely remove the nvidia driver. A format and clean install is the best way to go but if you don't want to do that you can use driver cleaner to remove the nvidia driver.
I have an MSI K8N NEO Platinum and an X800 Pro with zero problems.
It will work just fine. Just make sure you clean up the old vid card drivers really well.