First of all, I'm actually going to try to install to a SD card first but if that fails I will try USB. I'm guessing the process will be largely the same. Anywho, here is my situation:

I have an Asus eeePC 1005HA with Windows 7 and Ubuntu 9.10 installed on it. My hard drive also has a swap partition and recovery partition, which is why I can't install to the HDD (and to be honest, at this point I don't want to mess with that so I am opting to install BT to removable media). So, I already have GRUB installed on my hard drive. I want to install BT to either a 16 GB SD card or a 16 GB USB thumb drive.

However, I noticed that this guide directs you to install GRUB to the USB drive. Is this still what I want to do if I have already installed GRUB on my main hard drive and am currently dual booting?

What I want to happen is to have W7, Ubuntu, and BT all show up in the GRUB list at startup and be able to choose from the three. What I'm worried is going to happen is that I will have to go into my BIOS every time I want to run BT and tell it to boot from USB/SD and then it will load a separate instance of GRUB that will only have the one OS available.

So is it possible to have all three operating systems appear in one GRUB list, even though they are installed to different drives? If so, do I follow the same procedure outlined in that guide, or is there something different that I will need to do for my situation?

Thanks for any help in advance :-)