Boot Sector is same as MBR

[wckeyser]

I installed Win 7. Boot manager booted Win 7 OK.  Set up a new entry for Win XP.  Installed Win XP.  Re-enabled boot manager due to Win XP rewriting MBR. Booted Win 7 as a test.  Plop booted XP.  Tried again and booted Win XP.  Got the boot sector is same as MBR message.  Tried Win 7. Got the same message.  What am I doing wrong?