| wti | WebTranslateIt Configuration |
| wtp | Word2TeX Preferences |
| wxa | Buxco System Hardware Configuration Data |
| wzconfig | WinZip Configuration |
| x4k | XML4King Configuration |
| xaw | Xilinx ISE Architecture Wizard Settings Data |
| xbs | XnConvert Configuration |
| xc | RSNetWorx Configuration |
| xces | PDF-XChange Editor Settings Data |
| xci | Adobe LiveCycle Font Mapping Data |
| xconf | PTC Windchill Configuration |
| xcu | OpenOffice.org Configuration File |
| xee | Microsoft Expression Encoder Preset |
| xep | X-Genics eManager File Packaging Information |
| xfsf | BestSync Settings Data |
| xgc | GtkRadiant XML Game Config |
| xgi | XBCD Custom Settings File |
| xgs | XACT Global Settings |
| xiu | Chiasmus Configuration |
| xjb | JAXB Binding Customization |
| xjs | Jindent Settings File |
| xly | CMUD Settings Data |
| xpadder | Xpadder Settings Data |
| xpf | LMMS Presets Data |
| xss | Sorenson Squeeze Presets Data |
| xvm | VMware Server Console Configuration |
| xwk | Crosstalk Communicator Keyboard Mapping |
| xwms | WMS Server Connection Data |
| xxe_gui | XMLmind XML Editor GUI Settings Data |
| yardopts | YARD Settings |
| ysm | Yamaha Studio Manager Settings Data |
| yt | yt Project Configuration |
| zaf | ZoneCentral Access List Data |
| zap | Windows Software Installation Settings |
| zc | ZipKey Settings |