Ok mate. For the vast majority of us FC2 works just fine. I suggest that you calm down and take a deep breath. There are a lot of very qualified people around that will help you if you are polite and patient.
Do you have the latest chipset, video, sound card drivers for your devices?
Disk maintenance performed? Defrag/chkdsk?
Memory tested?
Did you remove all folders etc after your uninstall? Before the re-install?
Did you properly remove the Nvidia drivers before installing the new ATI drivers.
Have you confirmed that you have a good download of the product, no corrupt or mis sized or mismatched files?
Are you doing a default install or changing the path anywhere?
Is UAC on or off?
Are you running under an Admin account?
Full system specs?
AV/Security software running?
Have you tried a clean boot to rule out any other software as conflicting?
Sounds to me like you have a hosed install....Consider re-download of product?
More info, less rage and we can try to help you work this out.
Out