What is it?
xstor.dll is a library for Apache OpenOffice, an open-source office productivity software suite that contains a word processor, a spreadsheet, a presentation application, a drawing application, a formula editor, and a database management application. OpenOffice's default file format is the OpenDocument Format (ODF), an ISO/IEC standard.
Description of xstor.dll from OpenOffice.org
“Apache OpenOffice is the leading open-source office software suite for word processing, spreadsheets, presentations, graphics, databases and more. It is available in many languages and works on all common computers. It stores all your data in an international open standard format and can also read and write files from other common office software packages. It can be downloaded and used completely free of charge for any purpose.”