Cards are not "64-bit", it's the drivers that are 32- or 64-bit. Nvidia support both types in their graphics drivers.
However, I recommend to use the installer provided by your distro instead of downloading one from nvidia's website. That you get a slightly outdated version that way does not matter as the drivers already support the 8800 for years.
Oopsy, I only now noticed that this thread is in the "Open-Source NVIDIA" section. I'm not sure if that's really important to you or you just posted here by mistake. The official NVidia driver (which is not open source) fully supports the 8800GT as was mentioned already, but if you're asking whether the open source driver (called "Nouveau") supports it, and if yes, how well, then I don't know.