Well, you have to install the right ones. There are tons of them even if you are using the genuine kernel and not a distro version. Mandrake, Redhat, Gentoo and other distros sometimes make their own version, the original with some patches applied. You have to install the right one before it will work correctly.
It might also help if you told what distro you are using. You can post it or just put it in the userCP and it will be under your name, like mine is, I think it is anyway.
If you don't know for sure what kernel you are using, go to a command line, console or whatever you have and type in
It should look something like this:
root@smoker / # uname -r
root@smoker / #
Then just find the right ones and install them. You may have to link /usr/src/linux to the right directory too. Mine looks like this:
root@smoker / # ls -al /usr/src
drwxr-xr-x 7 root root 288 Aug 18 02:07 .
drwxr-xr-x 20 root root 656 Jul 29 03:51 ..
-rw-r--r-- 1 root root 0 Jul 20 00:15 .keep
lrwxrwxrwx 1 root root 23 Oct 31 2004 linux -> linux-2.6.8-gentoo-r10/ <--------------- THIS IS THE LINK <--------
drwxr-xr-x 18 root root 632 Jul 7 07:27 linux-2.6.12-gentoo-r4
drwxr-xr-x 18 root root 632 Aug 14 18:45 linux-2.6.12-gentoo-r6
drwxr-xr-x 18 root root 632 Aug 18 02:08 linux-2.6.12-gentoo-r9
drwxr-xr-x 18 root root 632 Aug 16 01:34 linux-22.214.171.124
drwxr-xr-x 19 root root 1320 Aug 14 18:45 linux-2.6.8-gentoo-r10 <---------- THIS IS WHAT IT LINKS TOO <-----------
root@smoker / #
Notice the forth one points to linux-2.6.8-gentoo-r10 as a link, the -> means it is a link, and the little "l" at the beginning of the line. That is the kernel that I am currently using. If I switched kernels, I would have to change the link to point to the right one. If it points to the wrong one, nvidia may not install correctly or at all.
You may also want to make sure it made that link when you installed the sources. Some do, some don't. Gentoo does the first time but after that, you have to make your own.
Try to see what you have and post back some info. Maybe me or someone else familiar with your distro can help.