Undoing WIndows 7 boot on XP system after trial?

I'm considering doing a free trial of Windows 7 on a system that currently dual boots XP 32 bit and XP 64 bit. I know that adding Windows 7 will add or replace NTLDR (and BOOT.INI?).

My C partition is free of any other software other than just the boot files, is there a way to back this up before installing Windows 7 to make undoing this easier?

If not, if I boot from XP cd-rom and go into recover mode, will fixboot (and fixmbr if needed) restore the boot process to XP style or will I need to do more?