Screenshot is taken by pressin the Print Screen button in keyboard.
Then u open MS Paint or IrfanView or any other Image editor an Paste the image.
Initially,that is while taking screenshot,it's size can not be specified,it will be as large as ur monitor.Then u can use IrfanView to reduce the size or resolution.(In IrfanView,use Edit>Resize/Resample option).
With print screen button, you can take screen shots without mouse pointers. If you want with mouse pointers, you need to use applications like ScreenHunterFree (382kb installation file) or printkey510f (558kb installation file). PM me with your email address if you want me to mail them to you
Print Screen will take screen shot of your full screen (With all windows and taskbar).
To take a screen shot of current application window only,
Select the Windows
Press [Alt] + [Print Screen]
Paste in any image editor as usual.