You cannot change the default width of the Outline or Slides panes in PowerPoint (285454)

WORKAROUND

To work around this behavior, select the panes that you want to appear when PowerPoint opens, manually adjust the size of the panes, and then save the presentation as the new default template.

To create a new template with the panes that you want and the width that you want each pane to have, follow the steps in the following example:

1. Start PowerPoint.
2. On the Tools menu click Options.
3. On the View tab, under Default view, in the Open all documents using this view box, select the default view that you want, for example Normal-thumbnails and slide.
4. Click OK.
5. Press CTRL+N to open a new presentation and verify that is the default view that you want.
6. Place your mouse pointer over the dividing bar between the left pane and the slide pane, and then reposition the divider bar to the width that you want.
7. On the Tools menu click Options.
8. On the View tab, under Default view, in the Open all documents using this view box, select The view saved in the file, and the click OK.
9. On the File menu, click Save As.
10. In the Save As dialog box, in the Save as type box, select Design Template.
11. In the File name box, type Blank, and then click Save.
    
    NOTE: Blank.pot is the only file name that PowerPoint recognizes as a default template.
12. On the File menu, click Close to close Blank.pot.
13. Press CTRL+N.
    
    A new presentation starts with your new template.