A number of readers have written to us mystified by a file-size anomaly in Microsoft Word. They'll take a relatively small document, embed a relatively small picture, and wind up with a file that's absolutely immense, 20 or more times as large as the combined size of the document and picture. Yet a different document and picture won't experience this uncontrolled growth.

This problem specifically affects Microsoft Word 2000, 2002, and 2003. It surfaces when a document containing an image in JPEG, GIF, PNG, or EMF format is saved in Rich Text Format or in Word 6.0/95 format. If the document is saved in Word's current format, the problem doesn't arise.

According to Microsoft, this is actually a feature. When the document is exported to one of those two specific formats, two copies of the image are included. One is the original image; the other is the same image converted to Windows Metafile (WMF) format. The WMF format is designed to describe resizable vector-type drawings—line drawings—and it's very efficient for those. But it's hideously inefficient at storing photographic images pixel by pixel.

Fortunately, a simple Registry tweak can turn off this "feature." Close all open instances of Word and launch REGEDIT from the Start menu's Run dialog. For Word 2003, navigate to the key HKEY_CURRENT_ USER\Software\Microsoft\Office\11.0\Word\Options. Word 2002 users should change 11.0 to 10.0; Word 2000 users should change it to 9.0. Look in the right-hand pane for a value named ExportPictureWithMetafile; you probably won't find it. If the value is not present, right-click in the right-hand pane and choose New | String value from the menu. Enter the name ExportPictureWithMetafile and click on OK. Then double-click on the newly created value, type 0 (zero) for its value, and press Enter. That's it: No more amazing expanding files. To put any existing bloated files on a diet, first save them in the current Microsoft Word format and then, if necessary, resave in the other format.