1. Go to nvidia website and download the compatible driver for your graphic card series.

2. prepare BT5 kernel sources
Code:
root@bt:~# prepare-kernel-sources
Code:
root@bt:~# cd /usr/src/linux
Code:
root@bt:~# cp -rf include/generated/* include/linux/
To install NVIDIA driver, of course, you must disable the Kernel Nouveau. Ok, letís start it from beginning.

3. Disable the Kernel Nouveau.
Code:
root@bt:~# echo options nouveau modeset=0 | sudo tee -a /etc/modprobe.d/nouveau-kms.conf
Code:
root@bt:~# update-initramfs -u
4. reboot

5. Make sure you are not in an X session (log out to console), and run the Nvidia driver installer.

To enter In tty1
Code:
ctrl + alt + F1
kill X session
Code:
ctrl + C
6. Install the NVIDIA driver

Example in my situation:
Code:
root@bt:~# sh NVIDIA-Linux-x86-280.13.run --kernel-source-path /usr/src/linux-sourve-2.6.39.4
7. Reboot your backtrack 5

Iím using 9800 GT in this case. I think, it should works on other series.

/mario cruz