Posting a screenshot on the forum
From MozillaZine Knowledge Base
Posting a screenshot when describing a problem is sometimes helpful. To do this, set up the programs the way you want them to appear in the screenshot, then:
Creating a screenshot
To take a screen shot of a single window, focus the window, then hold ALT while pressing the Print Screen key. If you need even finer control (or you don't have the privileges needed to create a screen shot) use a screen capture program such as MWSnap or PicPick that let you specify any rectangular area or a specific window.
On Vista and Windows 7 the Snipping Tool can be found in Accessories (Start Menu > All Programs > Accessories). For easy access later, right-click on Snipping Tool and pin it to the Start Menu. After invoking, select any rectangular area on screen and save it as a .png or .jpg file.
Most screen shot capture programs don't explicitly support capturing a popup menu. If you need to capture a popup menu trying to use the mouse to tell it to capture the current window will make the popup menu disappear. Your best bet is to use a screen capture program that lets you press a hot key to capture the current window. You need to use a hot key combination that doesn't use the ALT key to avoid problems due to Thunderbird using ALT shortcuts to open menus. One way to do that is to start the MWSnap program, minimize it, bring up the popup menu you want to capture, press Control+Shift+W, and then click on the popup with the mouse.
To take a screenshot of a single window, press Spacebar after pressing Cmd+Shift+4, then click the window.
Uploading for general use
Uploading for use on Bugzilla