Yes you can.

See these two threads for a lot of information about adding fans and related stuff

http://en.community.dell.com/owners-club/alienware/f/3746/t/19332001.aspx

 http://en.community.dell.com/owners-club/alienware/f/3746/p/19331658/19694335.aspx#19694335

I personally installed a blue-led Antec Tricool 2000rpm 120mm fan on the inside of the case right against the radiator, powered by the molex connector included with the fan. This pushes air from inside the case past the radiator and out the back, in the same way the stock radiator fan does. This installation was really really easy to do, and it reduced CPU temps by a few degrees (measured using CoreTemp). This particular fan has a speed control (H,M,L) and I have mine set to high - 2000rpm - all the time. I am happy with the results, and the blue-led looks really cool when I open the case. I can also see it from the top of the case when the vents are open.

I orginally installed a temperature controlled Antec 2000rpm fan, and hooked it up to the CPU_FAN connector on the top of the case. However, since the CPU_FAN speed is in step with radiator fan (both system controlled - not manually controlled), both fans increased at the same time when cpu temps rose, and I didnt see much if any temperature reduction. Perhaps if i installed that fan on another location in the case, I would see some difference, but I just havent been that adventerous.

In addition to the 120mm fan, I recently removed the factory CPU thermal paste, and applied Arctic Silver. I followed the manufacturer's instructions to the letter (vertical line for the i7 - http://www.arcticsilver.com/pdf/appmeth/int/vl/intel_app_method_vertical_line_v1.1.pdf) and immediately noticed a 2-degree drop in CPU temperatures. After maybe half the way through the 200 hour breakin period now, temps have dropped another degree or so.

Did you use the screws that came with the Antec Tricool 2000rpm or did you have to have some special long screws?

Thanks for your help!

The screws that came with the fan were not the right length. I had to dig around in the garage for some loooong screws, and found a couple that worked.

I also wrapped the connector cable and routed it near the mobo along the top of the case, as the molex is near the front of the system and the fan at the back, as I like the tidiness of the Alienware insides , and with the cable wrapped and tucked in, you'd never know this was an add-on.

At 2000rpm, I can hear just barely hear the Antec running even with the vents open

[EDIT]

Forgot to include my idle temps (Celsius) for reference. I am at BIOS OC Level 1 (3.2Ghz)

So you can see the fan and thermal paste reduced idle temps significantly, but under load the temps were not much different but the system fan didnt have to work so hard. I was surprised that the temps were close to the same under load - I expected them to be lower. I really should redo these tests, as I didnt really take a very disciplined approach with tight baselines and a solid scientific approach.

It comes with a 3-pin connector, and a molex adapter, so I could hook the same fan up to either the CPU_FAN connector or a molex.

Again, I chose the molex so I could use the speed control on the Tricool fan and not have it controlled by the system in sync with the radiator fan.

Did you need a molex adapter? From the picture it looks like the fan has a female and the alienware also has a female. Does the fan have a male end or does it come with a male adapter?

Yea im going to go with the molex too...It just didnt seem from the picture that they were compatible (both look female). But you had no problems so I ordered one of the Antecs :)

Thanks for the info.

The molex connector is clever in that it has both a male and a female end. The picture on the Antec site it is showing the female side, but the back part of it is the male where you plug into the power on your computer.

If anyone was reading this and was interested to know the outcome.....I ended up buying this fan http://www.newegg.com/Product/Product.aspx?Item=N82E16835103069.  I added it as the push fan on my radiator and hooked the connector to the CPU_Fan. Also I had to buy screws: #6-32  1 1/4 inch

I played WoW last night for about 3 hours straight to test the difference and here is what I got.....

Using HWmonitor Pre-Fan:

 Max Temps:

core 0: 66c

core1: 64c

core 2: 64c

core 3: 62c

Using HWmonitor with Fan:

Core 0: 57c

Core 1: 54c

Core 2: 55c

Core 3: 57c

So overall the added fan dropped my CPU temps by 5c to 9c across all cores!

Im happy with results.