Open My Computer.
On the Tools menu (or the View menu), click Folder Options (or click
Options).
Click the File Types tab.
In the Registered file types list, click the specific Office document type
(for example, Microsoft Excel Worksheet), and then click Advanced (or click
Edit).
In the Edit File Type dialog box, *check* the Browse in same window check
box (or check) the Open Web documents in place check box).
Click OK.