Does there exist an opensource app that can be used with GRUB to enable a computer whose BIOS doesn't support USB booting to boot GRUB, then let you select an option like "Boot from USB" or "Boot from PARIDE" that launches into a stripped-down Linux kernel whose only purpose in life is to read the bootblock from a USB or PARIDE drive and transfer control to it as though it were being booted by the BIOS itself?

Example:

(BIOS POST)

(hard drive MBR read by BIOS, GRUB launched)

GRUB displays choices:
1. Linux
2. XP
3. USB boot
4. PCMCIA boot
5. PARIDE boot

(user selects 3)

(boots into mini kernel with support for just about every meaningful USB controller and peripheral compiled in, probes for bootable USB devices)

(one bootable USB found: loads bootblock, transfers control, execution continues as though it were BIOS-booted)

(multiple bootable USB found: displays menu of bootable drives, then continues as per above with selected drive)

I need this because I have a Ramline 510 industrial tablet PC that I want to experiment with, but it doesn't support booting from anything besides IDE and floppy, and it's a major pain to disassemble it enough to temporarily connect a floppy drive to the motherboard (it has a header, but no space to permanently mount one) or remove the hard drive so it can be prepared by a different computer. It DOES have WinXP on it right now, and XP works with USB drives without drivers, so I CAN use it to get Linux onto it "through the back door" (I vaguely remember encountering a program about 9 years ago that let you boot into Slackware's installer from a paride CD or zipdrive by booting into Windows, putting the Slackware disc into the drive, then running a Win32 program that loaded the paride bootblock, killed Windows, and transferred control to the bootloader).

Any suggestions where to look first?