I downloaded the RC2 update to give the new features a shot. WinXP detected the new video drivers, none of which were signed (of course.) It gave me three to pick from and I took the one from the top of the list. Since then, it has had a driver conflict with the Parallels video driver and, although WinXP will boot, all that happens after the normal loading screen is a black screen. I'm pretty sure that if I could just force it to boot into safe mode, I could roll back the system to before the new drivers were installed and get it working again. However, I cannot find a way to force either the WinXP loader or the Parallels BIOS to force a safe mode boot.
And no, I was not smart enough to back up the file beforehand.
And no, I was not smart enough to back up the file beforehand.