What distro (Mandrake, Fedora, SUSE, etc.) are you running? Have you installed the Linux kerenel source package? If so, can you type:
Code:
cd /usr/src/linux<tab>
Type the above but press <tab> after typing 'linux'.
If that doesn't work then you'll need to install the kernel source.
Search LQ for how to do that for your distro.