First off, have you tried installing the Driver off of Nvidia's site, rather than using the one automatically installed by Ubuntu? They have Linux native drivers for both 32-bit and 64-bit. I'd try that out if you haven't already.
What do you mean by "but can't seem to install it..." I opened a terminal, typed in 'sudo apt-get install alsamixer' and it couldn't find the package. If this is the case, then a quick Google search will yield a direct download of the program. If you tried installing it via the downloaded program, what kind of errors/issues are you getting?