A new instance of Word appears to run when you create or open an additional document in Word 2000 and in later versions of Word

When you create or open an additional document, another instance of Word appears to run.

Note In earlier versions of Microsoft Word, when multiple documents are opened, only one Word button appears on the Microsoft Windows taskbar. However, in Microsoft Word 2000 and in later versions of Word, when multiple documents are opened, a separate button appears for each document on the Windows taskbar.

By default, versions of Word that are later than Microsoft Word 97 use the Single Document Interface (SDI) design, in which each document occupies its own window (just as in Microsoft Outlook each message occupies its own window). This behavior is different from Word 97 and earlier versions of Word, which use the Multiple Document Interface (MDI), in which each document is a separate window within the Word program window. SDI was introduced in Word 2000.

In the Single Document Interface, only one instance of the Word program (Winword.exe) is running. To confirm this, do either of the following to display the Windows task list:

• In Microsoft Windows 98, Windows Millennium Edition (Me), and Microsoft Windows NT 4.0, press CTRL+ALT+DELETE.
• In Microsoft Windows 2000 and in Microsoft Windows XP, either press CTRL+ALT+DELETE or right-click an empty area of the Windows taskbar and then click Task Manager.

Note In Microsoft Windows NT 4.0 and Microsoft Windows 2000, when you display the task list, you see every instance of an open document as a separate task on the Applications tab. However, when you click the Processes tab, you see one instance of Winword.exe running.

In Microsoft Windows 98 and in Microsoft Windows Millenium Edition, when you press CTRL+ALT+DELETE, the Close Program dialog box shows only one instance of Microsoft Word.

In Microsoft Windows XP, there is an option called Group similar taskbar buttons (right-click the Windows taskbar, and then click Properties). With this option selected (default), you can group multiple buttons into one button.

For additional information, click the following article number to view the article in the Microsoft Knowledge Base: You can start a second instance of Microsoft Word when you are using a command-line switch.

For more information, click the following article number to view the article in the Microsoft Knowledge Base: Because Word 2000 uses true SDI technology and no longer supports MDI, SDI cannot be turned off in Word 2000. Other Microsoft Office 2000 applications, such as Microsoft Excel 2000, can support MDI. Therefore, SDI can be turned off in those applications.

The ability to turn off SDI was added to Word in versions of Microsoft Office that are later than Office 2000. MDI is now supported in Word and in the other Office applications. This functionality is controlled by the Windows in Taskbar option.

To turn SDI on or off, follow these steps, as appropriate for the version of Word that you are running:

Microsoft Office Word 2007

1. Click the Microsoft Office Button, click Word Options, and then click Advanced.
2. Under Display, click to select (or click to clear) the Show all windows in the Taskbar check box.
3. Click OK

Microsoft Office Word 2003 and earlier versions of Word

1. On the Tools menu, click Options.
2. On the View tab, click to select (or click to clear) the Windows in Taskbar check box, and then click OK.

Benefits of SDI

The Single Document Interface provides the following benefits:

Improved navigation

Some users found the Window menu in earlier versions of Word to be counter-intuitive. Documents became "lost" behind other open documents, and document window management was confusing to use. Having each document in a separate window with a Microsoft Windows taskbar icon for each document makes navigation easier.

Improved performance in WordMail

Note This section does not apply to Word 2007. Word 2007 is the only e-mail editor in Outlook 2007.

The Single Document Interface makes it easier and more convenient to send messages directly from Word.

For additional information about Single Document Interface and Word 2000, Word 2002 and Word 2003, click the following article numbers to view the articles in the Microsoft Knowledge Base: