The Essential Guide to Dual Booting Windows

Want to run more than one version of Windows on your PC? It can be done -- but with care and caution.

InformationWeek Staff, Contributor

August 21, 2003

7 Min Read

Install NT/2000 on a 95/98/Me PC
Adding Windows NT or Windows 2000 to a machine that already has Windows 95, 98, or Me on it is much simpler than the reverse for one simple reason: Windows NT/2000 is smart enough to detect the presence of another operating system during installation and modifies its boot files accordingly. Because of this, if you install WinNT/2000 in a machine that already has another version of Windows on it -- and it doesn't matter what version -- you'll see an entry in the boot manager for both editions of Windows.

The installation procedure to follow when adding NT/2000 to a 95/98/Me computer isn't enormously different from installing NT/2K in general. There are, however, a few guidelines to follow.

1. Do not install NT on a FAT32 partition.
This is probably the single most important rule. NT supports only FAT and NTFS, not FAT32, and can't be installed on a FAT32 partition. In fact, it generally can't even read FAT32 partitions. So if you're planning to make data readable by both operating systems, be sure not to place it on a FAT32 partition. Place shared data either in a FAT partition or on a networked drive.

Also, do not convert a FAT16 partition that has NT installed on it. Converting a partition with NT installed on it to FAT32 will render it unbootable.

The sole exception to this rule is with Windows 2000. Win2K can read and write FAT32 partitions without problems. Installing Win2K on a FAT32 partition, however, means you won't be able to use NTFS security features on your system partition.

2. Don't use disk compression.
In fact, this is a global rule: Never use disk compression on any multiple booting system. It's not worth it, and it creates more problems than it solves. Most drives today are big enough that disk compression is contraindicated, anyway. Windows Me won't even install onto a system that has disk compression running.

3. Do a disk check before an installation.
Lingering disk errors can cause terrible problems later on down the line when you install an operating system. During Windows installation, there's a disk check; don't skip this step.

4. Always use a discrete partition for other operating systems.
As with installing Win 95/98/Me on an NT/2K system, this rule also applies here, and for the same reasons. Installing one Windows application set over another can cause horribly unpredictable things to happen. In most cases it will break IE and Outlook Express, and if shared .DLLs are overwritten, it may cause other apps to malfunction, too.

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Each operating system should always reside on its own partition for the best possible results. Here, a FAT32 partition has been prepped for a new installation of Windows Me.

If you want to share applications between operating systems, the best way to do this is to install the app on one OS, boot the other OS, and then reinstall it into the exact same folder. However, a few applications may not work correctly if you do this: for instance, any application that uses CTL3DV2.DLL or CTL3D32.DLL, since there are discrete versions of those .DLLs for 95/98/Me and NT/2K. Your safest bet is to install apps in separate partitions, although a few programs can be coaxed into running without being reinstalled.

Another thing to be aware of when adding a new partition to a Windows 9x machine is how Windows 9x translates partitions as drives. In some cases, if you add a partition, you may break your drive-lettering scheme and possibly render your Windows 9xsystem unbootable.

Here's an example of this: On a computer that had two primary partitions, C: and D:, I had Windows NT on C: (which was marked as bootable) and Windows 98 on D:. When I added a third, logical partition, the drive lettering was thrown off and D: turned into E:, making Windows 98 unbootable.

There are two simple ways to defeat this. One is to use only primary partitions (a maximum of four per hard drive) and to add them in sequence. Another is to add Windows 9x last whenever you set up a system, to preserve the integrity of the drive mapping. The downside of this method is that it goes against the common wisdom of putting 95/98/Me on a system first, so this is recommended with some reservations. Forcing Win9x to map drives a certain way is difficult and not always successful. (Windows NT and 2000 let you map drives any way you like and are not as prone to this problem.)

Third-party Programs for Multiple Booting
Sometimes the easiest thing to do in multiple boot scenarios is to let someone else take control of the whole process. The Windows NT/2K multiple boot loader is not simple to configure and has no easy way to add operating systems that aren't directly supported. If you're booting between more than one OS, or various revisions of OSes, the boot loaders you have may not be enough to do the job.

Boot loaders work in a couple of different ways. Some of them are installed in a special partition, only a few megabytes in size that is marked as bootable. When that partition is booted, the boot loader program takes over and presents the user with a menu of possible boot choices. Usually the program analyzes the available partitions at each boot, to determine whether anything has changed since the last boot.

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System Commander works with just about any PC-based operating system to let you choose the OS you want to boot.

The best third-party boot loader out there so far appears to be System Commander from Vcom. System Commander automatically detects any changes made to your PC since the last boot and updates its menus automatically to reflect those changes.

The makers of the aforementioned PartitionMagic also have a multiple boot manager program named BootMagic, which does many of the same things as System Commander and supports Windows 2000 as well.

VMware is another way to run multiple OSes on the same system, but without using multiple booting. Instead, VMware creates a virtual computer console on your PC -- basically, a computer within a computer. The virtual computer runs at about two-thirds the speed of your real computer and has access to many of the same resources -- disk drives, printers, network, etc. This allows you to run one or more operating systems, as many as you can devote disk space for, without having to reformat a drive partition or play around with dualboot settings.

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VMware lets you run a 'virtual computer' in your computer, letting you install any operating system you choose. But it'll only work in NT or Windows 2000 and needs plenty of memory. did a full review of VMware, which discusses many of the strengths and weaknesses of the program. One main weakness: it runs only under Windows NT or Windows 2000, and it won't work in Windows 95, 98, or Me. VMware also needs a lot of memory and processing power to get good results: On anything less than a Pentium II 400, it crawls, and it needs at least 128MB of RAM to really work well. You can try before you buy, though; the official site contains instructions on obtaining a 30-day trial license via e-mail.

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