File extensions that begin with W.

 Ext.  Type of file
 WAB   Windows (Outlook) address book
 WAV   Windows audio
 WAX   Windows Media playlist

 WB?   Quattro Pro spreadsheet (?=version)
 WBK   Microsoft Word backup
 WBT   WinBatch file

 WCM   WordPerfect macro

 WDB   Microsoft works data file

 WGP   Wild Board games data

 WID   Font width table
 WIF   Wavelet image
 WIN   Window file (misc. apps)
 WIZ   Microsoft Word wizard

 WKQ   Quattro spreadsheet
 WK1   Lotus ver. 2.x
 WK3   Lotus ver. 3.x & Windows
 WK4   Lotus ver. 4.x
 WKE   Lotus educational version
 WKS   Lotus 1-2-3 ver. 1a spreadsheet

 WMA   Windows Media audio
 WMF   Windows Metafile
 WMS   Windows Media Player skin
 WMV   Windows Media video
 WMZ   Windows Media Player skin

 WOA   Windows swap file

 WPD   Corel WordPerfect
 WPD   Windows printer description
 WPF   WordPerfect form file
 WP?   WordPerfect document (?=version)
 WPG   WordPerfect raster & vector graphics
 WPL   Windows Media client-side playlist
 WPM   WordPerfect macro
 WPS   Microsoft Works document
 WPT   WordPerfect template

 WQ?   Quattro Pro for DOS (?=version)

 WRI   Windows Write document
 WRK   Symphony spreadsheet
 WRL   VRML page

 WS?   WordStar for Windows (?=version)
 WSC   Windows script component
 WSD   WordStar 2000 document
 WSF   Windows script file
 WSH   Windows Script Host properties

 WTV   Windows TV (Media Center DVR)

 WVL   Wavelet compressed file
 WVX   Windows Media playlist