Dual OS Installation of WindowsXP 32-bit/64-bit

Source
Page 1: Dual OS Installation of WindowsXP 32-bit/64-bit
Page 2: Why do I need a second partition?
Page 3: Installing Windows XP x64 Edition as a dual-boot
Page 4: Dual OS Installation 101
Page 5: Enjoy your dual 32-bit/64-bit system!
Page 6: Un-doing a 32/64-bit dual-boot
Page 7: Editing the Boot.ini file

If you'd like to keep Windows XP x64 Edition installed, but want the 32-bit version of XP to be the default operating system selected at bootup, open the BOOT.INI file as described above and replace the multi(0)disk(0)rdisk(0)partition(1) settings of the 'default=' line with those of the 'Microsoft Windows x64' line. Your BOOT.INI file should now look something like this:

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect
multi(0)disk(0)rdisk(0)partition(2)\Windows="Microsoft Windows x64 " /fastdetect

Microsoft Windows XP 32-bit will now load by default.
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wrote:

1. Boot from Windows XP32 CD; select new installation.
2. On the screen that shows the disks and their partitions, the drive letters will be C: and E: on the first disk, and D: and F: on the second disk, because Setup enumerates primary partitions first, then logical drives in the extended partition.
3. Install in the first partition on the second disk.
Do you want to? If you use Microsoft dual boot, all four partitions will be visible.
If you install into the default Program Files folder, there won't be any conflicts.
As long as you don't do anything stupid, you'll be fine.

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Use boot manager to dual-boot between 32- and 64-bit
Serdar Yegulalp, Contributor

The most commonsense way to transition between 32- and 64-bit editions of Windows is to dual-boot between the two systems. However, even though both are versions of Windows (and in theory they're the same versions of Windows), they install different boot tools that may render dual-booting difficult.

The 32- and 64-bit editions of Windows use two files loaded at boot time to recognize Windows system files: NTLDR and NTDETECT.COM. The 32-bit Windows edition of these files only recognizes 32-bit editions of Windows—or, rather, it can only correctly boot 32-bit editions of Windows. The 64-bit boot loader can recognize 32- and 64-bit editions of Windows.
As a result, if you install the 64-bit edition on a given system and then install the 32-bit edition in such a way that the boot files are replaced, you'll no longer be able to boot to 64-bit Windows unless the boot files are repaired. This can be done from the 64-bit Recovery Console with the FIXBOOT and FIXMBR commands.
However, a better option is to use a third-party boot manager to segregate each edition of Windows onto its own separately-booted partitions. This way the boot loader for each OS is kept discrete, and they won't overwrite each other.
One program I've used myself is Terabyte Unlimited's BootIt Next Generation. (The program costs very little per-seat to use and also comes in a free trial version.) Using a program like this, you can install 32-bit Windows on one partition, temporarily mark it as inactive, install 64-bit Windows on the other, and then use BootIt to choose which partition to start from at boot time.
Note: Windows Vista, in both its 32- and 64-bit editions, has a new boot-loader mechanism that is apparently even less user-friendly then the existing BOOT.INI system.
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How-to-hide-partitiondrive-in-Windows
Dual boot with Windows XP and two separate Linux installations