I have XP32, XP64, and linux installed on my main PC. However, I'm using the GRUB boot loader that came with the linux install.
All Windows partitions were created with gParted in order to get proper sector alignment. XP32 was installed first, then XP64. I don't remember if XP64 added XP32 to the boot menu. I think maybe it did not.
After that, I installed linux. The boot loader from linux (grub2) detected the 2 Windows installs and put them both on the boot menu along with linux. I then had to use linux to change the default boot option to XP64 (which is what I almost always use).
The setup was complicated by the fact that XP64 supports GPT partitions *after* booting, but cannot boot from them. XP32 doesn't support GPT at all. I wanted to utilize the full capacity of a 4TB drive, so I ended up with a weird setup involving MBR partitions on a 1TB drive and GPT partitions on the 4TB (which XP32 can't access). XP64 boots from an MBR partition on the 1TB but everything else for XP64 is on the 4TB.
dr_st wrote:So, if you first installed XP 32-bit and then XP 64-bit, won't the 64-bit's boot loader be able to recognize both installations, and allow you to choose them via boot.ini, like any pair of NT5.x OSes?
It's a vague memory but I think my XP64 install superceded XP32. I hope I'm wrong about that though and it would be worth trying.
If it doesn't work automatically, then I suppose it should be fixable, but I don't know what's involved.