In order to install the nvidia graphics drivers on BT5 you need to enter the following into a terminal prompt while X is not running.
First you need to prepare the kernel sources if you have not done so already by:
Please remember to copy and paste these commands into your terminal prompt as formatting can make long lines wrap over into two or more lines !
apt-get update
apt-get install linux-source
prepare-kernel-sources
cd /usr/src/linux
cp -rf include/generated/* include/linux/
cd /
Then for 32bit BT5: following the prompts
wget http://us.download.nvidia.com/XFree86/Linux-x86/270.41.06/NVIDIA-Linux-x86-270.41.06.run
chmod +x NVIDIA-Linux-x86-270.41.06.run
./NVIDIA-Linux-x86-270.41.06.run
Or for 64bit BT5: following the prompts
wget http://us.download.nvidia.com/XFree86/Linux-x86_64/270.41.06/NVIDIA-Linux-x86_64-270.41.06.run
chmod +x NVIDIA-Linux-x86_64-270.41.06.run
./NVIDIA-Linux-x86_64-270.41.06.run
And that's it, you should now be able to restart, startx and enjoy the full glory of BackTrack at the full resolution offered by your graphics card and monitor.