Diskeeper is a professional disk defragmenting tool with versions for both 9x and NT. It includes features such as scheduling and background defragmentation.

Diskette Manager, from BLOC publishing, previously from Lassen Software, is a software tool for the IBM PC and Tandy that inventories the contents of your floppy disks in to a database. It enables you to quickly and easily search for files or print disk labels.

DiskLock, From Fifth Generation Systems, and later from Symantec as Norton DiskLock, is a data security tool that can lock a hard disk or individual files or directories so that it requires a password to access any data. It can also log activity to detect unauthorized access attempts. It also features the ability to lock the system after an idle usage period. There were versions for PC and Mac.

Disney Animation Studio is an animation graphics tool, that originated on the Amiga. It supports multiple VGA resolutions.

DisplayWrite is a word processor that is based on the IBM Displaywriter dedicated word processing system. It directly competed with software ports of dedicated word processors such as the Wang Word Processing System (or its clone MultiMate ), Lanier Word Processing Software, Xerox, DEC, or similar.

Delrina DosFax is a DOS based program for sending and receiving faxes via a modem that has fax capabilities. This software was often bundled with modems or PCs. It was often accompanied by Delrina WinFax.

Helix/Double Helix is an easy to use relational database for the Apple Macintosh. It features a visual programming system, and options for multiuser over AppleTalk.

First released in 1989, DoubleDisk was the first real-time drive compression product for DOS. It is a fairly no-frills program and sticks to what it does best. It was relatively low cost compared to its later competitors. and Expandz! Plus

DoubleDOS is a simple and easy to use multitasking tool for DOS. It can preemptively run up to two DOS programs at a time. Its main advantage is that it requires very little RAM overhead compared to other multitasking or task switching environments. Because DOS programs can and usually do bypass OS calls, many programs must be "patched" in order to work. things at once, then this would have been a good choice. Reportedly, the first version may have worked with DOS 1.x.

DoubleTools is a set of Windows-based utilities that adds functionality to DoubleSpace, included with MS-DOS 6.0.

DR Draw is a shape-based drawing program that uses Digital Research's GSX graphics library, making it portable across CP/M and DOS architectures with different video systems.

DR Graph is a business graphics creation program. It can create line, bar, pie, and scatter graphs and print them on a graphics printer. DR Graph is implemented using Digital Research's GSX graphics library, and can run on many different platforms.

Dr Halo, by Media Cybernetics, is a DOS based image editor. It was sometimes distributed as a value-added tool with mice or video cards. Its image editing capabilities were fairly weak, and its main strength came from its adaptability to new hardware, positioning it mainly as an entry-level product provided with new hardware.

Dr Solomon's Antivirus was a top rated commercial virus scanning suite. There were versions for DOS, Windows 3.1, 95, 98, Novell, SCO Unix, Solaris, and OS/2.

Dr. Sbaitso is a simple AI program, similar to the famous "Eliza", that makes use of text-to-speech software. Distributed as a demonstration application with Creative Labs Sound Blaster cards.

Drafix is a powerful, high performance, and feature rich 2-dimensional computer aided design tool. Despite being a 2-D CAD program, it had many features of high end 3-D CAD software, and competed directly with AutoCAD. Drafix was first was fist released in 1986 for DOS, and was the first professional CAD program released for Microsoft Windows.

DrawPerfect, from WordPerfect Corp., is a vector based drawing program with graphing functionality used for making slides and presentations. It was later replaced with WordPerfect Presentations

DS Backup Plus is a simple hard disk backup utility. It was not as full featured or robust as other backup products, but it got the job done. Backups can be done from within the program or from the command line. It supports wildcards, filespec inclusion/exclusion, backup to any DOS drive type, automatic disk formatting, incremental backups, and claims to be faster than DOS backup and restore.

DS Manager is a menu and file management shell for DOS. It features password protection with the ability to display different menus for different users.

DS OPTIMIZE is a disk defragmenter tool. It has a few more options than its competitors, and has a "fast" mode that does not protect against interruptions. This tool competed against Mace Utilities, The Norton Utilities, PC Tools, and many smaller defragmenter tools.

DS Recover, from Design Software, is a set of file utilities for DOS that lets you unerase files and directories, and unformat disks. It competed against the Norton Utilities, PC Tools, and Mace Utilities.

DS Squeeze, from Design Software, is a file compression tool. It features a full screen file manager with a directory tree. Although it is not a tool that compresses an entire drive, it boasts the ability to launch executable files even after they are compressed.

DVMpeg, from Darim Vision Co., Ltd, is an MPEG encoder that can convert Windows AVI files to MPEG.

EagleCalc is an electronic spreadsheet for working with tabular data consisting of 255 rows and 64 columns. It was based on Lattice Inc's Ultracalc, a spreadsheet for CP/M systems, and designed to emulate VisiCalc and Microsoft Multiplan.

EagleWriter by Lexisoft is a word processing and office management package that offers flexible print format and output capabilities, macro capabilities, and ease of use. EagleWriter is customized for the Eagle computer function keys and help feature.