Hi and Welcome to Just Answer,
Ok we can take a look at this,
The question is kinda lost, so I am going to give 3 answers
A window frame will expand to fill the entire desktop when you:
A. double-click the taskbar.
B. double-click the horizontal scroll bar.
C. click the title bar button marked with two overlapping squares.
D. click the title bar button marked with a single square.Answer is D
Thanks Maria For the Assist
2. You are wanting to Maximize your screen
If you are talking about the windows frame for windows, Right click on the title bar and click Maximize.
Thanks Smithy for heads up
3. You are wanting to extend your Wallpaper
If you are talking the desktop do the following
Start ->Control Panel ->Display ->Desktop
Click on the drop down in positioning and click on "Stretch"
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If there is anything else let me know, If not click accept. Thank You Michael L.