The easiest way is probably to simply open the DOC document in latest Microsoft Word and save it in DOCX format. Other word-processors might be able to achieve same thing.
Found 2 different conversion types using the same filename extensions.
Conversion doc to docx type 1:
Convert from Microsoft Word document (prior version 2007) to Microsoft Word Open XML document.
Microsoft Windows software - convert doc to docx on Windows
A popular word processor that started with Word for MS-DOS in 1983 and for year is now a core application of Microsoft Office suite. Microsoft Word offers powerful word processing and text editor features that allow users to easy create high quality documents.
File type (from-> to)
Convert from doc file
Microsoft Word document (prior version 2007)
|Yes, Microsoft Word supports doc file conversion as a source file type.||Yes||Yes||doc editor||Yes||No||No||No|
to docx file
Microsoft Word Open XML document
|Yes, Microsoft Word supports docx file conversion as a target file type.||Yes||Yes||docx editor||Yes||No||No||No|
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned doc to docx. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
AbiWord is a free cross-platform word processor that is part of GNOME office suite. AbiWord is unique among word processors in its drive to become a fully cross-platform word processor.
All File to All File Converter 3000 is universal converter for pictures and documents. It is able to convert formats like PDF, Microsoft Word, Excel, PowerPoint, TEXT, HTML, JPEG, GIF, TIFF etc.
Atlantis Word Processor is an application that will help you to work under extremely safe conditions. Atlantis is an innovative, no-nonsense word processor carefully designed with the end-user in mind.
iStonsoft ePub Converter creates ePub eBooks from PDF, MOBI, HTML, Word, Text. It is a simple and powerful ePub Builder and designed to provide you with the easiest solution to build your own ePub eBooks.
TextMaker is popular text editor and word processor that comes as part of SoftMaker Office. It contains many features and supports all current major document formats.
TextMaker is also licensed to other office suites, such as Ashampoo Office.
A full office productivity suite on various operating systems. Kingsoft Office suite provides Kingsoft Writer, Kingsoft Presentation, and Kingsoft Spreadsheets - three basic and essential applications for users.
Microsoft Publisher is entry-level desktop publishing application used to create brochures, newsletters, postcards, greeting cards, or e-mail newsletters. Microsoft Publisher is distributed with some editions of Microsoft Office suite.
Apple macOS / Mac OS X software - convert doc to docx on OS X
Microsoft Word for Mac is the Macintosh version of the popular word processing application from Microsoft Office Suite. It offers powerful text editing features for both home and corporate users.
The latest version of this application, Microsoft Word, is integral part of Microsoft Office for Mac and cannot be bought as standalone.
AbiWord is a popular, open-source word processor and text editor that is available mainly for Windows and Linux, but there is also version for Mac OS X. It is a native port with slightly slower update cycle.
NeoOffice is an office productivity software for Mac OS X created as an alternative to OpenOffice.org. It has everything needed for common office including word processor, spreadsheet, presentation program, and graphics program.
iWork Pages is popular word processor for Apple Mac OS X and iOS operating systems. It is a part of iWork office suite. Pages can be also used as a page layout application. Apple distributed Pages with 140 document templates for creating letters, résumés, posters, and outlines. Pages can open documents from Microsoft Word, AppleWorks, Rich Text, PDF and EPUB.
Linux/Unix software - convert doc to docx on Linux
AbiWord is a popular, open-source word processor and text editor that is available mainly for Windows and Linux.
KWord is an open source text editor and word processor mainly meant for Linux platform but also with support for other platforms. It offers many handy features and clean interface. KWord comes as part of KOffice.org office software bundle.
Windows Mobile/CE software - convert doc to docx on Windows Mobile
Microsoft Word Mobile helps you with creating and editing of your Microsoft Word documents directly on your Phone. Word Mobile (in previous versions of Office Mobile, known as Pocket word) is part of Microsoft Office Mobile, that is automatically loaded in Windows Phone based smart phones and accessible in the Office hub.
Word Mobile does not fully support all features included in Microsoft Word for desktop computers. However you will be still able to open the documents on your found phone, but the unsupported content won't be visible.
SoftMaker Office for Windows Mobile is a all-in one mobile office solution for smart phones based on Windows Mobile platform. It is able to perform all basic tasks with documents, spreadsheets and presentations directly on your phone. It seamlessly supports Microsoft Office files and PDFs.
Symbian software - convert doc to docx on Symbian
OfficeSuite allows you open and edit most common Microsoft Office documents directly on your S69 powered smartphone. The latest version of OfficeSuite also supports the XML based Microsoft Office formats, such as DOCX or XLSX.
Apple iOS (iPhone, iPad, iPod Touch devices) software - convert doc to docx on iOS
Apple Pages for iOS brings the famous Pages for Mac OS X to your iOS based devices such as iPad, iPhone or iPod touch. It offers excellent mobile office solution with beautiful design and many powerful features. It is available in Apple app store.
Google Android software - convert doc to docx on Android
OfficeSuite Professional is a productivity application for Android smartphones, that allows users to open and work with Microsoft Office documents, PDFs or other common document formats. It has many handy features which makes it a great mobile office solution.
Blackberry mobile phones and devices software - convert doc to docx on Blackberry
eOffice is a set of productivity apps for BlackBerry devices. eOffice Solution was selected as a Regional Selection in the 2010 BlackBerry Partners Fund Super Apps Developer Challenge! It is able to to View, Edit, Create & Share Microsoft Office 2007 files including Word Documents, Excel Spreadsheets, PowerPoint Presentations.
Multiplatform software - convert doc to docx on any platform
Powerful converter for Google Drive service.
LibreOffice Write is a complete word processor and document publishing tool that supports a plethora of document formats and has many innovative features. It's an open source software that comes as an integral part of LibreOffice suite.
Apache OpenOffice Writer (OpenOffice.org Writer) is a fully-featured and free word processor and text editor from OpenOffice.org productivity suite.
Apache OpenOffice Writer is simple enough for a quick memo, yet powerful enough to create complete books with contents, diagrams, indexes, etc. You're free to concentrate on your ideas while Writer makes them look great.
On-line services software - convert doc to docx on web
Docs is a web word processor from Google and part of Google Docs and Google Drive on-line services. It is a free alternative to other word processing software, accessible to any user with Google Drive account.
Conversion doc to docx type 2:
Convert from Document file to Microsoft Word Open XML document.
Microsoft Windows software - convert doc to docx on Windows
Word Excel to Htm Html Converter is one of the many conversion programs available from Allimagetool.
WordPerfect is a word processor developed by Corel. Originally was released for MS-DOS, later ported to Unix and Mac. The latest versions are programmed for Microsoft Windows and it is a part of Corel WordPerfect Office suite.