This can be very userful and I do it almost everyday when working on my website.
Open the application, website or file you wish to take a snap shot of.
Press the Print Screen key on the keyboard as shown. Your capture is now
stored in memory.
Open a paint program such as Photoshop or MS Paint. Now make a new file:
File>New and click OK. Now go to Edit>Paste to paste the capture in the
new document. When you get this far, move to "Cropping the image" below.
Cropping the image
Sometimes we want to remove application interfaces or backgrounds from the image.
This can be done in Photoshop.
After you paste or load the image in photoshop,select the rectangular marquee tool.
Now make a selection around the area that you want to keep.