The new Latitude D820 covers just about every base that a great business laptop can, clearing the way for us to call it one of the best midsize corporate portables around.

Specifications

Processors
Intel®  Core®  Duo Processor 
Up to T2600 (2.16GHz Dual) L2 Cache 667MHz FSB 
Great for the highest performance in multi-
tasking environments now and in the future. 
Explore the benefits of Notebook Processors

Operating System
Genuine Windows® XP Professional
Enjoy the benefits of SP2 - Service Pack 2
Dell offers systems which run Genuine Windows®  XP and are capable of running Genuine Windows®  VistaTM . For more details on Dell systems that can run Genuine Windows®  VistaTM .

Memory
Dual Channel DDR2 Shared Memory
DDR2 is a memory architecture that enables systems to improve performance and reduce power consumption. The amount of RAM you have determines how many programs can be executed at one time and how much data can be readily available to a program.
Available DIMM Slots:
Two Memory slots offering up to 4GB
Memory Bandwidth:
667MHz - 8.5 GB/s with dual channel - Improves performance
Performance Professional User:
2GB or more for Intensive simultaneous business applications with headroom for future OS/Applications
Mainstream User:
1GB or more is recommended for business users running multiple simultaneous office applications

Graphics
512MB NVIDIA®  Quadro NVS 120M TurboCacheTM
High end graphics solution specifically designed for graphically-demanding applications like 3D modeling and video-editing. Delivers scalable flexibility for investment protection.
256MB NVIDIA®  Quadro NVS 110M TurboCacheTM
The 256MB NVIDIA Quadro NVS 110M offers all the latest graphics technology to produce extraordinary visual effects, robust wide-aspect LCD support and compatibility with all major business applications.
Intel®  Graphics Media Accelerator 950 (Up to 224MB shared)
The GMA 950 graphics core is an intelligent and responsive graphics engine built into the chipset that is on the motherboard. This integration provides incredible visual quality, faster graphics performance and flexible display options.

Displays
WUXGA (1920 X 1200 resolution) WSXGA+ (1680 X 1050 resolution) WXGA (1280 X 800 resolution)

Hard Drives
SATA - also known as Serial ATA
Benefits of the SATA drives offered on Latitude notebooks: Password protection feature on the HDD. A password must be entered before the HDD can be accessed and the system boots. This provides an extra layer of data security.
Faster, Improved data integrity, and Improved scalability
Capacities up to 120GB1

Additonal Features
POWER:
Power Supply:
90 Watt AC adapter with cord wrapping
Batteries featuring ExpressChargeTM :
Primary 9-cell/85 WHr
Secondary 6-cell/48 WHr "Smart" Li-Polymer battery 
CONNECTIVITY:
Wired:
Wired: 56K v924 Internal Modem 10/100/1000 Gigabit Ethernet2 network interface adaptor
WLAN
Intel®  3945 WiFi 802.11a/g, Dell Wireless 1390 802.11g, Dell Wireless 1490 802.11a/g Dual-Band Mini-Cards, Internal Bluetooth (optional)
EXPANDABILITY:
PC Card:
One Type I or Type II
Express Card:
One 54mm Express Card slot, supporting both 54mm and 34mm I/O
Ports:
Serial, docking connector, USB 2.0 (4), Powered USB (D/Bay), 1394, VGA, headphone/speaker out, integrated microphone, infrared port, RJ-11, RJ-45, AC power
Docking:
D/Port, D/Dock, D/View Notebook Stand, D/Monitor Stand, D/Bay
Modular Options:
24X CD-ROM, 8X DVD+/-RW3, 24X CDRW/DVD4, Floppy Disk Drive, Secondary 6-cell Battery, 80GB Hard Drive
USB Memory Keys:
128MB, 256MB and 512MB USB Memory Keys (optional)  SECURITY:
Physical Security:
Cable Lock Slots, Media Module and Hard Drive Locks.
User & System Security:
Integrated Smart Card Reader, Trusted Platform Module 1.2 and optional UPEKTM  finger print reader. Wave Embassy®  Trust Suite by Wave Systems security software.
Network Security:
802.11 WiFi Protected Access (WPA), 802.11i (WPA2), Virtual Private Networks (VPN) and 802.1x with EAP modes and compatible with CCX 4.0

Review

Pros:very fast, light weight, great screen, long battery life
Cons:nvidia quadro nvs 120 is fast but not fast enough to play 3D games like Oblivion over ~75% quality
Full user opinion
The D820 packs the most amount of performance in a 6.5 lbs laptop that you could possibly squeeze into one with its size. The advantage of this computer is that you get a ***t load of battery life (with a 9 cell battery). You’re more boring aka business tasks like excel and word will yield an unconditional 5 hours of battery life, watching movies will give you around 4 or so...I haven’t tried playing Elder Scrolls Oblivion while on battery, so I couldn't tell you. I know a lot of people have been asking about the D820’s graphics card, it’s comparable to an ati x1400 and an nvidia geforce go 7400. Yes the game is playable and it looks GREAT but the graphics card is brought to its knees at max quality. Yes I know this is a "business" lap top, but if you are like most people, you want to know you can play games, because when the day is over, you spent a few thousand dollars on a laptop computer and you want to know you can get your moneys worth. Besides, windows vista will be released soon, and I hear it is a graphics BEAST. Don't even get me started on how important your graphics card will be with that operating system.

Source:
http://reviews.cnet.com