FileInfo.com - The File Extensions Resource

.XPD File Extension

File Type 1	XML Pipeline Document (Most common)
File Format	File
Common?	No
File Description	Web page generated from an XML document, usually via an XSLT transformation; developed by Joshua Tauberer to power GovTrack.us and other websites
Program(s) that open xpd files	Mac / Windows: Any Web browser

File Type 2	PlayStation Store PSP License File
File Format	Proprietary File
Common?	No
File Description	License file downloaded along with content from the Sony PlayStation Store; used for Digital Rights Management (DRM\\|rm) and required to transfer games and other downloaded files to the PlayStation Portable (PSP) device. XPD files are acquired by the PlayStation Network Downloader (PSND) when downloading files from the PlayStation Store for PSP.
Program(s) that open xpd files	Windows: Sony PlayStation Network Downloader

Information from FileInfo.com - The File Extensions Resource.
http://www.fileinfo.com/extension/xpd