I would just borrow a WinXP CD from anyone you know and install it using the serial # under the unit.
Btw, what does the Trusted Platform Module (TPM) do?
Unfortunately, just borrowing someone's XP CD won't work, because you'd have retail code with a VLA/OEM prod key. If it even let you past the prod key screen, the Windows Genuine Advantage nagware would definitely fail.
You should be able to burn the entire i386 folder to a CD and run winnt to start an install (note: not just the contents of i386, but the entire i386 directory, so you'd run winnt out of cdromroot\i386).
As for the TPM, it holds your Storage Root Key and does the number crunching for AES encryption using the Client Security Solution.