As requested by "SoftwareDefinesRadio", here is the tutorial on how to dual boot BT2 and BT3. I think I got the BT2 folder name right, however, this is just from memory, and I gave my last BT2 disc away, so if it's wrong, let me know and I'll correct it. Hope this doesn't count as a double post, because the other tutorial was at the end of a thread that might end up getting lost, and I figured this would be a more appropriate place. If it is, let me know, and I will cite a reference in the other thread instead of a tut. Enjoy!

1. Off the backtrack disc, copy over the 'boot' and 'BT3' folders.
2. In the 'boot' folder, run the "" file.
3. Verify that this has installed BT3 correctly, and then proceed to step 4.
4. Copy over the 'BT' folder from the BackTrack 2 disc, and the 'boot' folder, but rename it 'boot2' or something similar.
5. Using your favourite editor (be it notepad, gedit, kedit), open (from your flashdrive) "boot/syslinux/syslinux.cfg". This is the menu for the BackTrack 3 startup, and we will edit this to reference to BT2.
6. Add this line to your "syslinux.cfg" file, assuming you used boot2 for the directory.

LABEL bt2kde
KERNEL /boot2/vmlinuz
APPEND vga=0x317 initrd=/boot/initrd.gz ramdisk_size=6666 root=/dev/ram0 rw chexpand=256 autoexec=xconf;kdm

7. Providing you leave the BT2 main directory the same (BT), and in the root of the USB, then this should boot appropriately.
8. Reboot and test. That's all!