WinXP 64-bit and Win2000 dual boot

Possible incompatibility (not fully verified)

I found that after installing Win2000 on my 64-bit AMD chip (long story about HP PC crashing and losing XP 32-bit), and then installing Windows XP 64-bit, everything seemed to work great. I was able to boot into Windows XP and set it all up.
But after rebooting and trying to start Windows 2000, it blue-screened with a "Stop 0x0000007B" error.

I did notice a lot of web pages describing that the installation order is important because each Windows OS installs itself and it's version of ntldr and ntdetect.com. I just didn't think that it would break Windows 2000.

Previously, I had WinXP 32-bit, then installed WinXP 64-bit, and both ran fine together.

I repaired my Windows 2000 partition by copying back the Win2000 ntdetect.com and ntldr.