Use Faststone Capture software! According to me it is the best screen capture and editing tool,it can capture scrolling windows too that is all what you need!
read about it's all features!
it can easily and very fastly join 2 pictures vertically or horizontally!
If any query,then comment! :)
A small handy Capture Panel that provides quick access to its capture tools and output options
Global hotkeys to activate screen capturing instantly
Capture windows, objects, menus, full screen, rectangular/freehand regions and scrolling windows/web pages
Capture multiple windows and objects including multi-level menus
Record screen activities including onscreen changes, speech from microphone, mouse movements and clicks into highly compressed video files (Windows Media Video format). A built-in video editor allows you to draw annotations, apply zoom effects and cut unwanted sections
Options to specify output destination (internal editor, clipboard, file, printer ...)
Draw annotation objects such as texts, arrowed lines, highlights, watermarks, rectangles and circles
Apply effects such as drop-shadow, frame, torn-edge and fade-edge
Add image caption
Resize, crop, rotate, sharpen, brighten, adjust colors ...
Support tabs that allow you to capture and edit multiple screenshots simultaneously
Support external editors
Save in BMP, GIF, JPEG, PCX, PNG, TGA, TIFF and PDF formats
Acquire images from scanner
Convert images to a multi-page PDF file
Join images side by side to produce a single image file
Send captured images by email
Send captured images to Word and PowerPoint documents
Send captured images to a Web (FTP) server
Screen Color Picker
Support multiple monitors
Support touch interface (tap, swipe, pinch)
Run when Windows starts (optional)
Minimize to System Tray area
Small footprint in memory
And many more ...