New I7 CPU has very low Windows Experience Index
Check the temperatures before and when running some demanding program. The CPU may be throttling. I've seen laptops which were unusable due to too aggressive throttling settings.
Another option may be aggressive power saving modes. First plug the laptop in and make sure the battery is full. Then set it to highest performance and try again, just to be safe.
Anyway, it's a great CPU, so the behavior definitely isn't to be expected.
About the update: No, it is not plausible at all. WEI may be affected a bit by other applications, but not this much and unless you have say 1 GiB of RAM or less, RAM shouldn't be a major problem. Also I can't see how Windows installation could be faulty in such way to affect the speed of the processor that much. The only thing that could have such an effect other than BIOS and hardware would be various applications for performance control. I don't know what Dell ships so I can't give specific advice, but it could be that one of them sets the processor into a low power consumption state.
Just to be sure, restart the computer, close all background applications after computer boots and run the WEI again and see if there's any change. In my experience, the change is limited to ±0.1, but it might be different in your case.
Also, just to be safe, a virus scan may help, but I don't think that such behavior could be caused by infection.
Can you please post a screenshot of CPU-Z's CPU tab? It'll give us some more data about what is actually going on with the processor.
Look at the scores of each component on the WPI report. The WPI total score is actually the lowest score from any of the components (Processor, Graphics, Hard Disk, etc.).
Whatever is giving you the lowest score, is where your problem is.
Make sure you are running it with the laptop plugged into AC power, and with all other applications closed. Running it on battery, will result in an artificially lower score.
I was having a similar issue with a new M4600 that had an i7 2820.....was getting a 3.7 on the WEI processor score. Disabled Intel SpeedStep in the BIOS...re-ran the assessment...got a 7.4.