Reinstall Backtrack it will work afterwords.
I was running windows vista and I had hdd installed back track 5 r2. When I was booting my PC there were option to boot either operation system. After I installed windows 8 preview version that menu does not appear anymore. I tried to boot from cd and after startx loading screen appears but jumps back to black screen where write startx. I kinda remember I had this problem before and had solved but not sure how was it?
FYI: hp dv9000 core 2 duo 2.81 gpu disabled cuz fried
I agree with Sickness. Backtrack must be lastly installed. If you can configure ur menu to not boot previous MBR it would help. Or configure to not rememeber last boot.