Mastering Multibooting Madness

I often dream of a future Windows NT. An NT that has evolved into the über-OS: An NT on which I can run not only essential business and productivity applications but also run multimedia applications, develop applications, and operate my favorite aerial combat simulator. Although this dream is growing closer to reality, NT doesn't provide this functionality yet. Several applications don't run under NT 4.0, and NT 4.0 lacks support for popular hardware technologies such as Universal Serial Bus (USB) and APIs that Microsoft included in Win9x (e.g., DirectX 5.0 and 6.0). These shortcomings make NT users feel left behind, and although Windows 2000 (Win2K) promises to cure most of NT's ills, this promise doesn't help current NT users.

You're lucky if NT 4.0 supports all your applications, but you might still need to install and run more than one OS (e.g., if you're a developer or network administrator who needs to run applications under multiple versions of Windows for compatibility testing). Whatever your reason for running multiple OSs, getting them to run happily on the same PC can be challenging. Read on for tips, tricks, and tools that you can employ to help manage a multi-OS environment.

NTLDR: NT Boot Central
When you install NT, the OS sets up an NT-specific Master Boot Record (MBR) on your first hard disk's primary partition. When you first start up a PC, NT Setup automatically loads the MBR, then passes control to NTLDR. NTLDR parses the boot.ini file from the root of the NT system partition and uses boot.ini to generate a list of OS boot selections. (For more information about NT's boot process, see Mark Russinovich, "Inside the Boot Process, Part 1," November 1998.) Boot.ini contains the OS boot options that NT is aware of, which usually include NT-related entries but can also include entries that point to other OSs. The boot.ini file's [Operating Systems] section lists each NT-related entry and uses an Advanced RISC Computing (ARC)-style path to describe the relative disk location of each entry. On a system running only NT, the [Operating Systems] section lists at least two entries: one for a normal NT boot and one for a VGA-mode startup configuration, which boots NT using a plain-vanilla VGA video driver. Your boot.ini file's [Operating Systems] section might look like

[Operating Systems]
multi(0)disk(0)rdisk(0)partition
  (1)\winnt="Windows NT
  Workstation 4.0"
multi(0)disk(0)rdisk(0)partition
  (1)\winnt="Windows NT 
  Workstation 4.0 [VGA mode]"
  /basevideo /sos

If you want to install additional OSs on your PC and you want to use NT's boot loader to access them, the following factors affect how you'll proceed:

• If you've already installed NT, how you formatted the primary system partition, which is the partition from which the system boots (e.g., FAT16 or NTFS)
• Which OS you want to install
• Which partition you want to install the OS on
• Which partitions you want each OS to be able to access

These factors are important because every OS has a set of supported file systems and quirks and variations in the disk partition configurations and OS locations it supports. For example, you can install NT on a primary or extended partition (i.e., a logical drive within an extended partition), but you can install DOS and Win9x only on a primary partition. In addition, NT can handle drives that contain multiple primary partitions, but these configurations cause problems for DOS and Win9x. Table 1 shows the file systems and accessibility types that common OSs support.

To determine which file system to use on a partition, you must consider which OSs will require access to the data you store on that partition. If you store important Microsoft Word and Excel documents on an NTFS-formatted drive, you can't access those files when you're booted under Win98. In addition, from an NT installation, you can't see data you store on a FAT32 volume under Win95 OEM Service Release (OSR) 2.x or Win98. (You can use add-ons from Systems Internals to read and write to FAT32 volumes from NT installations. For a list of related products, see "Multibooting Resources.") So, why don't you use FAT16 on all partitions in a multiboot system? The answer is that by doing so, you sacrifice disk space and performance because FAT16 uses larger cluster sizes and less efficient data-retrieval techniques. However, FAT16 might be your only option.