get it on screen, then press your 'print screen button'
Then pick programs>accessories>paint
then choose Edit>Paste
then use the little box in the left hand toolbox to choose the section you want and choose 'edit>copy'
then choose 'file>new'
then choose 'edit>paste'
save the result as a .jpg to your hard disk, and then post it to a image hosting site like
www.imageshack.us
then post the link as an image on wherever you want to post it