Resizing & Cropping Images
There are two ways that you can change the size of an image — resizing and cropping.
Resizing changes the dimensions of the picture by stretching or shrinking it.
Cropping reduces the size of the picture by removing the vertical or horizontal edges. Cropping is often used to hide or trim a part of a picture, either for emphasis or to remove unwanted portions.
If you’re sure you won’t need to undo your changes after you crop the picture, use the Compress Pictures feature to delete the cropped parts of the picture from the file completely. This helps shrink the file size of your documents.
Cropping Images
PowerPoint is probably where you’re most likely to crop images, but you can also do this in Word and Excel if you need to.
1. Select the picture you want to crop.
2. On the Picture toolbar, click the Crop button 
.
NOTE If the Picture toolbar is missing, click Toolbars under the View menu,
and then click Picture.
3. Position the cropping tool over a cropping handle and then do one of the following:
» To crop one side, drag the center handle on that side inward.
» To crop equally on two sides at once, hold down CTRL as you drag the center handle on either side inward.
» To crop equally on all four sides at once, hold down CTRL as you drag a corner handle inward.
4. On the Picture toolbar, click the Crop button 
again to turn cropping off.
Here’s how to crop an image in Office 2010
[...] that even after using PowerPoint’s option for compressing the pasted images, the file size was still larger than the file using inserted images. Share [...]
[...] I’ve been using this approach for almost five years now, sending a short (and hopefully sweet) tip via email every Friday morning. They are meant to be quick and easy to “get” within just a couple of minutes and the topics are usually driven by questions I get asking for help or useful shortcuts that I think can save people some. For example,this morning’s tip is about cropping images in Microsoft Office. [...]