I recently received a new Dell D820 and the hard drive is very slow. I updated all the drives to see if that would help, nope. I have an external drive with a Hitachi 2.5” drive in it that I purchased from newegg which is a faster drive than what dell ships, but I think something is just plain wrong with the drive dell has chosen to put in the D820’s. I took the drive out of the external enclosure and rebuilt the laptop with it. Below is the difference in speed as told by HDTach.

The blue line is the original hard drive dell shipped with the D820 and the red line is the new drive I dropped in there. What a difference; average speed is higher and just look at the difference in burst speed. Finally I have a laptop again that can run VM’s, no thanks to Dell.
UPDATE: The new drive I dropped in is a 7200 rpm drive which accounts for some of the performance increase. I have another benchmark on an ATA100 5400rpm drive that is still faster than the Dell D820 stock hard drive, so I still believe there is something wrong with the drive Dell ships with these laptops.