USB drive boot manager

Hi /prog/

I have windows installed to one HDD, and *nix to another. ATM i use the BIOS to switch between drives at boot. This is because I want each drive to remain bootable on its own [eg if i brick one of the two OSes]. Obviously this isn't very efficient.

I'd like to have a boot manager installed on a USB drive to select between which to boot, but I want to avoid doing anything that modifies the drives so that they become unbootable without the USB stick either.

Can you point me in the direction of some software that can do this? I've looked at Plop, YUMI, GRUB and LILO but i'm not really sure which best suits my needs, and if its possible to use them in the way i describe [from USB stick, with USB keyboard and without modifying their MBR etc].

>>16
I was just looking into SYSLINUX as it happens; as with grub its not exactly super-easy and filled with disconcerting caveats on every other line. Still, if its not hard its not worth doing (apparently).

I considered what you describe with the *nix drive, but again, the situation I'm concerned about is when I have to remove the drive with the bootloader. then I'm back to having to use the BIOS (eg if i want to choose between 2 windows drives). If anything what I want is to be able to remove the USB [boot manager] drive so I can go back to using the BIOS to select boot device in worst case scenario without any HD being unbootable.

>>13
Thanks, I've been doing some searching along those lines for a little while, unfortunately as with most *nix topics, the assumption is that I have been using it all my life and that its not as easy as one wrong command to brick everything. I've used it a little in VMs (mostly backtrack and k/ubuntu) but this is the first time I've installed it (PC-BSD) properly.

I'll do some more searching and post anything useful/confusing as it arises I guess.