I own an M200. You're probably not going to be able to to boot from USB. You can boot from SD, but it's tricky too; the built-in SD firmware only does SD, not SDHC. They're also very picky about what external USB CD/DVD drives they'll boot from. I have the docking base with a built in DVD combo drive, and it's what I used for installing anything.
Also of note: M200s are extremely slow at booting from an external optical. There's some sort of BIOS bug that causes it. Booting a Win7 DVD took over an hour (the RC was even worse). Getting through the text-mode setup of XP is an exercise in patience.
If you have the patience to figure out PXE booting (and have a spare system to act as the server), this may be the best (and most flexible) route to go.