The Matrox DualHead2Go
Laptops may support dual external monitors, but without a stand-alone graphics card, their resolution leaves something to be desired. Another alternative is to use a USB connection for additional displays, such as the Sitecom USB2VGA adapter we tested last year. But because of bandwidth limitations, this solution's video playback and 3D graphics suffer from a noticeable flicker effect.
Enter the Matrox DualHead2Go, which uses a special graphics driver that doubles the horizontal resolution of the secondary or auxiliary graphics output. The small DualHead2Go box processes the signal from the VGA output and divides these signals up so that the image output stretches across two displays. Output resolutions of 1024 x 765 or 1280 x 1024 thus translate into 2048 x 768 or 2560 x 1024. One half of the screen image shows up on the first external monitor, and the DualHead2Go sends the other half to the second external monitor.
The DualHead2Go lacks a built-in graphics processor, which is why it won't work with an older notebook. Indeed, to produce an image in parallel to the one on the internal TFT with such wide resolution through an external output, graphics hardware is absolutely essential. That probably explains why the initial (and very short) list of compatible notebooks has only been recently expanded; you can find a current version of the compatibility list on Matrox' Website.