I'm going to tell you an another trick
Of taking screenshot from windows 7
through a simple method.
For this purpose we have to use a one tool that is already present in our windows 7.
The First is to ;
i) Click on start button.
ii) Now in the Search box, type Snipping Tool and select the snipping tool showed in results of search.
iii) It will open a new box like pop-up.
This will a show a snapshoot of your entire screen .
Next step is to save that file.
vi) Click on save file at the left top corner
Open dialouge box will be appear choose the Correct place where you wanna save your screenshot.
MAIN POINT
while saving this ,, open dialogue box would have selected different formats of saving file
but you have to cancel .png or something .. just click on below box of formats
& select jpg or jpeg & then Save the file