When I installed Backtrack 5 R3 I chose to dual boot, and it completely erased my BIOS and installed GNU Grub as the first thing that shows up when I boot up. The "Press escape for startup options" still shows but if I press escape it says BIOS is missing or corrupted. I would like to boot to the windows installer from my USB stick (Testing out windows 10), remove GNU Grub, and flash back my BIOS while still being able to dual boot to Backtrack 5 R3.
Ok I finally figured it out. My BIOS actually was corrupted so I replaced the BIOS chip, booted to recovery console from recovery disk, and then fixed my MBR. I can finally boot into something other than windows and backtrack! Not sure how to get into backtrack now though since it just boots straight into windows, but that's not important. Thank you PM 2Ring for your help!
I found the answer over on SuperUser.
At the Grub menu press "C" to get to the Grub command line. Typing ls at the command prompt will list the devices grub has found.
Of course it may be difficult to determine which drive is the USB stick you want to boot. You can ls within the devices to try to figure that out.
grub> ls (hd0,1)/
Once you find the proper device, set it to root.
grub> set root=(hd0,1)
Or the older syntax:
After setting root, enter these commands do boot using the bootloader on the device:
grub> chainloader +1 grub> boot
This should work with any bootable disk.