well maybe you can use that not so cool but working solution
extract grldr and menu.lst to c:\
add this line : c:\grldr="backtrack" at the end of boot ini
edit c:\menu.lst >>> edit it according to your install details( add a "bt start" menu entry)
when windows boot's up hit F8 for boot menu
choose "backtrack" normally grub will appear with proposing "bt start", hit you've done it...
THAT WORKS.....BUT I HATE THIS SOLUTION YOU NEED TO USE MICROSOFT PIECE OF CODE TO BOOT BT, IT'S A SHAME I THINK, BUT IT WORKS