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. This is a subject I'll cover in a future tip. But I will note here that beta testers have reported that the best thing to do is install Vista in a completely dedicated system whenever possible, and not dual-boot.)
About the author: Serdar Yegulalp is editor of the Windows Power Users Newsletter, which is devoted to hints, tips, tricks, news and goodies for Windows NT, Windows 2000 and Windows XP users and administrators. He has more than 10 years of Windows experience under his belt, and contributes regularly to SearchWinComputing.com and SearchSQLServer.com.
More information on this topic:
- Tip: Configuring a PC for dual-boot mode
- Topics: Admin tools
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