Why the hell am I getting this message when installing driver?

So I was running my NVIDIA GeForce 6600 perfectly for almost 3 years. My bro gave me an ATI Radeon graphics card of his (not sure of the model, 7300 GT?), so a couple hours ago I uninstalled my NVIDIA graphic drivers, and removed the graphics card. I put in the ATI card, booted up, etc.

Here is the message I get when installing the ATI driver:


Warning

Setup was unable to find components that can be installed on your current hardware of software configuration. Please make sure you have teh required hardware of software.

OK


So I said screw that and put my old 6600 back in, downloaded the drivers again, etc. I figured the ATI card isn't compatible with my motherboard, understandable.

Now I'm getting the following message:


NVIDIA Setup Error

The NVIDIA Setup program could not locate any drivers that are compatible with your current hardware. Setup will now exit.

OK


It makes absolutely no sense how the original card is having issues when no modifications were made to my computer in two hours!

Thank you in advance for your help.

Also, 7300GT is an Nvidia card... so, you may have downloaded the wrong drivers. I would make sure you:
1. Have the right drivers.
2. Use Driver Cleaner to remove all the old stuff.
3. Install new hardware (graphics card)
4. Boot up and DO NOT let Windows locate the drivers for you. (Just cancel that process and install the driver package your self*)
5. Reboot and you should be good.

*I have noticed that the Windows "Plug and Play" attempt to install the graphics drivers often ends in failure, or by pointing to the correct drivers your self, getting this "Setup was unable to find components that can be installed on your current hardware of software configuration. Please make sure you have the required hardware of software. "