apt-get install linux-kernel headers did the job.

I did the

# make-kpkg --append-to-version=-310505 kernel_image

And then got an error. I tried doing it again and about half and hour later it finished doing it. (no errors this time though a lot of warnings)

I did the

# dpkg -i kernel-image-your_version_name.deb

No errors. Went to see what's in the grub config file and it seems like Knoppix added bunch of lines on its own. Here's the file now:

title Debian GNU/Linux, kernel 2.6.11 Default
root (hd0,1)
kernel /boot/vmlinuz root=/dev/sda2 ro ramdisk_size=100000 init=/etc/init lang=us apm=power-off nomce quiet vga=791
initrd /boot/initrd.img
savedefault
boot

title Debian GNU/Linux, kernel 2.6.11.11-310505
root (hd0,1)
kernel /boot/vmlinuz-2.6.11.11-310505 root=/dev/sda2 ro ramdisk_size=100000 init=/etc/init lang=us apm=power-off nomce quiet vga=791
savedefault
boot

title Debian GNU/Linux, kernel 2.6.11
root (hd0,1)
kernel /boot/vmlinuz-2.6.11 root=/dev/sda2 ro ramdisk_size=100000 init=/etc/init lang=us apm=power-off nomce quiet vga=791
initrd /boot/initrd.img-2.6.11
savedefault
boot

### END DEBIAN AUTOMAGIC KERNELS LIST
title Windows 2K/XP/2003 (sda1)
chainloader (hd0,0)+1
The first one's the old one that I always used. The second one is the new one.The third ones a backup (I guess) and the fourth entry is Windows.

Reboot.

Grub menu comes up. I select and boot from Debian GNU/Linux, kernel 2.6.11.11-310505.

error message [kernel panic]

audit (somenumbershere) initialized
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block (8,2)


Reboot.

I select the 'old' entry and boot from that. Works. Guess what though? Instead of waiting for knoppix to load for 30 seconds, like I always do, it booted in 10-15.

What did just happened?

Back to the real problem though: installing the nvidia drivers. I'll try doing it now... Maybe it will work? Who knows...