| .D0 | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .D01 | Yamaha Corporation | File audio | OPL2 FM Audio File | Winamp with Ganbatte! Plug-in | Unknown Developer |
| .D2D | Unknown Developer | File di CAD | 3D Fassade Plus CAD Data | 3D Fassade Plus | Unknown Developer |
| .D2J | Unknown Developer | File sviluppatore | D2jsp Script File | Unknown Software | Unknown Developer |
| .D2R | Unknown Developer | File di giochi | Dazzle Dazzle Realization File | Dazzle Dazzle Realization | Unknown Developer |
| .DA! | Unknown Developer | File vari | Uncommon File Extension | Unknown Software | Unknown Developer |
| .DA0 | Microsoft Corporation | File backup | Windows Registry Backup File | Should Not Be Opened Manually | Unknown Developer |
| .DA5032 | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DAB | Epigon Media Technologies | File audio | Digital Audio Broadcasting Audio Data | Unknown Software | Unknown Developer |
| .DANGER | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DARBY | Unknown Developer | File vari | Uncommon File Extension | Unknown Software | Unknown Developer |
| .DATAGRABBER | Apple | File di dati | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .DATALESS | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DATALINKHE | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DATE | Apple | File di dati | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .DBU | Unknown Developer | File di dati | Client-Course Manager Database Expansion Update | Unknown Software | Unknown Developer |
| .DBX | Microsoft Corporation | File vari | Outlook Express E-mail Folder | Formula Graphics | Unknown Developer |
| .DB_ | Unknown Developer | File di CAD | CAD File | Unknown Software | Unknown Developer |
| .DCHB1 | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DDA | MicroImages | File grafici | TNTmips Import File Format | Unknown Software | Unknown Developer |
| .DDI | Unknown Developer | File con immagini disco | DiskDupe Disk Image | Unknown Software | Unknown Developer |
| .DDO | Unknown Developer | File di giochi | Tank3D Game Data | Unknown Software | Unknown Developer |
| .DE | Interscape | File con layout di pagina | DrawExpress Diagram File | Unknown Software | Unknown Developer |
| .DEFAULT | Apple | File di dati | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .DFA | Unknown Developer | File di dati | Amateur Strip Poker Data | Amature Strip Poker | Unknown Developer |
| .DFCOMPONEN | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DFI | Unknown Developer | File di font | Digifont Outline Font Description File | Unknown Software | Unknown Developer |
| .DFINE | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DFM | Open Source | File di testo | Pascal File | Unknown Software | Unknown Developer |
| .DHI | Unknown Developer | File di dati | DriverHound Index File | DriverHound | Unknown Developer |
| .DHR | Apple | File di dati | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .DIH | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DISPOSITIO | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DJE | Unknown Developer | File audio | MattBatt iAM-player Track List | Unknown Software | Unknown Developer |
| .DK | Unknown Developer | File vari | Danish Text/localization File | Unknown Software | Unknown Developer |
| .DLFA | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DLR | cebas Visual Technology | File con plugin | FinalRender Plugin | TIB Browser | Unknown Developer |
| .DMJ | Unknown Developer | File vari | Dustman Selection for Delete File | Unknown Software | Unknown Developer |
| .DMV | Adobe Systems Incorporated | File di settaggi | Adobe Acrobat Catalog Data | Unknown Software | Unknown Developer |
| .DNA.XML | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DNAXML | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DOCS | Unknown Developer | File di testo | Document | Unknown Software | Unknown Developer |
| .DOCUMENTAT | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DOO | Atari Corporation | File con immagini raster | Atari Doodle Image | Unknown Software | Unknown Developer |
| .DORE | Unknown Developer | File vari | Dore Raster Files Format | Unknown Software | Unknown Developer |
| .DOV | Safer Networking Ltd. | File vari | Temporary (Temp) File | Original Program That Created The File | Unknown Developer |
| .DOWN | Apple | File di dati | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .DOYO000 | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DP | Stefan Hagel | File di testo | Text Document | Unknown Software | Unknown Developer |
| .DR9 | Unknown Developer | File vari | Directory Files | Unknown Software | Unknown Developer |
| .DRAFT | Apple | File di dati | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .DRAGONSFUN | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DRIVE | Apple | File di dati | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .DRIVERS | Apple | File di dati | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .DRN | Unknown Developer | File di dati | Darn for DOS Data File | Darn software | Unknown Developer |
| .DRY | Unknown Developer | File di dati | XAIRON Organizer Diary File | XAIRON Organizer | Unknown Developer |
| .DRZ | Unknown Developer | File con immagini raster | Draz Paint File | Unknown Software | Unknown Developer |
| .DR_ | Unknown Developer | File vari | Compressed DRV File Of VFW | Unknown Software | Unknown Developer |
| .DSJ | Unknown Developer | File vari | Uncommon File Extension | Unknown Software | Unknown Developer |
| .DSSC | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DST- | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DTED | Unknown Developer | File grafici | Digital Terrain Elevation Geographical Data File Format | Unknown Software | Unknown Developer |
| .DTR | Swisslog | File di dati | Swisslog Downtime Analyzer Report | Unknown Software | Unknown Developer |
| .DUC | Datel | File di giochi | Action Replay Max DS Save File | Unknown Software | Unknown Developer |
| .DUPLICATEZ | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DVDREGIONC | Unknown Developer | File vari | Unknown File Type | Unknown Software | Unknown Developer |
| .DVDRIP | Unknown Developer | File video | DVD Disk Image | Unknown Software | Unknown Developer |
| .DWV | Unknown Developer | File vari | WAV File | Unknown Software | Unknown Developer |
| .DYNAMO | Apple | File di dati | Golden Orchard Apple II CD Rom File | Unknown Software | Unknown Developer |
| .D_ | Unknown Developer | File audio | Seqmax Seqprest Compressed Audio File | Unknown Software | Unknown Developer |
| .D_3 | Unknown Developer | File di dati | Polytext Ma'archot Meida Co. S"TaM | Unknown Software | Unknown Developer |
| .D_T | Unknown Developer | File vari | Eru/erd File | Unknown Software | Unknown Developer |
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