Problems with WinXP 64-Bit install

I’m wondering if anyone can offer a good explanation for problems I have experienced with
installation of WinXP 64-bit (AMD64 machine).

I have a bunch of tools for embedded development that I was reluctant to put on 64 bit OS still in
beta. So I decided to have regular 32 bit WinXP as primary installation and put 64 bit XP for
testing.

I split my 200 GB hard drive as follows:
C: 20 GB for 32 bit XP - FAT32 (old habits die hard)
D: 20 GB development - NTFS
E: 140 GB tools - NTFS
F: 20 GB for 64 bit XP - NTFS

I installed 32 bit XP and then tried to set up 64 bit OS. It passed text part of the setup, but
after reboot it halted saying “ntldr not found”.
After poking around, playing games with partitions and restoring 32 bit OS from the image I came
out empty handed. The darn thing did not boot.

Out of curiosity I removed all partitions, repartitioned it again and repeated my experiment. Same
result.

After all that I swapped partitions and put 64 bit XP on C: and 32 bit one on F:
Aside from 32 bit OS blindly replacing newer 64 bit ntdetect.com (another hour to repair)
everything installed and worked fine.

Can anyone explain a possible cause of this trouble?
Did partition format change with XP64? PowerQuest Drive Image 2002 failed to work complaining
about unknown partition format and its DOS counterpart displayed partition type for C: as FAT32X.

Any pointers on how to avoid similar problems in the future will be highly appreciated.
Thanks,
– Max.