Official Windows 98 Installation Media Formats

When Microsoft launched Windows 98 in June 1998, the personal computer market was transitioning rapidly from magnetic storage to optical discs. To accommodate varying hardware configurations of the era, Microsoft officially made Windows 98 available on two distinct physical media formats: CD-ROM and 3.5-inch floppy disks. This overview examines these official distribution formats, their packaging options, and how users deployed the operating system.

CD-ROM (Compact Disc)

The primary and standard distribution format for Windows 98 was the CD-ROM. Available through both retail channels and original equipment manufacturer (OEM) distribution, optical media offered the storage capacity required for the operating system's expanding feature set, multimedia files, and Internet Explorer integrations.

  • Retail Editions: Sold in both "Upgrade" and "Full Version" boxed sets, the CD contained the entire operating system setup, supplementary utilities, and optional system components.
  • Boot Capability: The original release of Windows 98 on CD was not directly bootable on most systems, requiring an accompanying MS-DOS-based setup floppy disk to load CD-ROM drivers before installation. When Microsoft launched Windows 98 Second Edition (SE) in 1999, the CD-ROM was made natively bootable using the El Torito optical disc standard.

3.5-Inch High-Density Floppy Disks

For users whose computers lacked an optical drive, Microsoft officially offered Windows 98 on 3.5-inch high-density (1.44 MB) floppy disks. Because of the sheer size of the operating system, this was not the preferred method of distribution and was primarily available as an upgrade edition obtained via special mail-in fulfillment coupons included in CD boxes or through select retail orders.

  • Disk Count: The floppy version required an extensive set of 38 to 39 disks. The set included setup disks and sequential media containing cabinet (.CAB) compressed archive files.
  • Distribution Media Format (DMF): To minimize the total number of disks required, Microsoft formatted the disks using its proprietary Distribution Media Format (DMF). DMF increased the capacity of standard 3.5-inch high-density floppies from 1.44 MB to approximately 1.68 MB per disk by altering track and sector layouts.

Windows 98 represented the final consumer-oriented release of Microsoft Windows to officially offer a complete floppy disk installation option, as subsequent releases exclusively required CD-ROM or DVD media.