The Dell Latitude D820 is most comparable to the D620's. The most recognizable difference is screen size and overall weight. The D820's are 15.1" and weigh slightly more. The D620's are 14.4 and weigh about a pound and a half less than the D820.
The Latitude D820 is equipped with the latest Intel® Centrino® Duo Mobile Technology: an available dual-core Intel® Core™2 Duo processor, choice of Intel 945 GM or 945 PM chipset and Intel PRO/Wireless 9345 Wi-Fi® mini-card.
The Latitude D820 features an available 512MB NVIDIA® Quadro® NVS 120M TurboCache graphic card.
D820's also feature magnesium-alloy casing and steel hinges and patented Dell StrikeZone™ technology.
The D820 released with the NVidia Graphics Chipset was recalled due to overheating and major component failure. More information can be found NVIDIA GPU Update: NVIDIA Class Action Settlement and Limited Warranty Enhancement
Fix common issues with your Latitude D820 here.