Your computer shouldn't be set up to launch Word when you click a jpg.
To fix this, open Windows Explorer, click Tools > Folder Options, go
to the File Types tab, click the JPG icon, and select a graphics
program such as Paint or the excellent free program from
www.irfanview.com.

The alternative is to right-click the jpg in the email and use Save As
to save the file to disk. Then use Word's Insert > Picture > From File
to insert the picture in a Word document.

Regards,
Jay Freedman
Microsoft Word MVP         FAQ: http://word.mvps.org