DAC 
Daisy-chain 
DAT 
Data 
Data bus 
Database 
Date-time 
DDE 
Decay 
Decimal 
Dedicated 
Default 
Deferred printing 
Definition 
Defragmentation 
Delete 
Delimiter 
Demo 
Density 
Desktop 
Desktop background 
Desktop icons 
Desktop publishing, DTP 
Desktop taskbar 
Desktop video 
Destination object 
Device 
Device driver 
Dial 
Dialer (or Phone Dialer) 
Dial-up connection 
Dialogue/dialog box 
Digital 
Digital monitor 
Digital signal processing (DSP) 
Digital to analogue convertor (DAC) 
Digital Video Interactive (DVI) 
Digitise 
DIR 
Direct cable connection 
Directory 
Disk 
Disk compression 
Disk controller 
Disk crash 
Disk tools 
Display adaptor 
Dissolve 
Dither 
DMA (Direct Memory Access) 
Domain 
DOS 
Dots per inch (dpi) 
Double-click 
DoubleSpace 
Double-speed drive 
Drag and drop 
Drive 
Drive letters 
Driver 
Drop-down menu 
Dynamic Data Exchange (DDE) 
Dynamic Link Library (DLL)