Microsoft changed the underlying graphics architecture between XP and Vista/7. When using Vista/7 you should have the latest Vista/7 compatible graphics drivers installed. The Vista/7 graphics driver can be referred to at the WDDM driver.
When running in WDDM mode, the Vista/7 display can either be in Basic mode or Aero Glass. The difference between these two modes is shown below:
DisplayLink recommends customers use Aero glass mode to avoid rendering issues in some applications.
The following youtube video gives a good summary of how to enable Aero graphics mode.