Also I had ask a similar question like that which someone was able to answer for me about. this might also help.

I had to reinstall windows once, but from what I hear the cd dell send you is just a regular windows cd. I think its best to confirm this with alienware-Milena.

I used this method which work fine for me. But first you need to confirm if you are booting you windows  UEFI. Im no pro but I was told that computer with UEFI have windows key directly embedded inside so if you do you computer will automatically detect the key.

1.First you need either blank cd or USB drive with 4 gb minimum.

2.I recommend USB, that's how I did it. I was also told that you cant us a CD to install widows on the UEFI which I believe is also where the alienware logo will be. if you want it to load like that but also for the key to be detected( im not sure if the key will be detect on the other booting option)

3. Microsoft gives free digital copy the cds for those that only needs the cd or usb to reinstall windows. I will post a link directly from Microsoft at the bottom of the page.

4. once you setup the usb or cd. which ever you chose. start up your computer and press f 12. From there you will chose if you want windows on the UEFI or the other normal booting mode. I used a USB for that so I have no Idea how it will be for the cd.

5. the rest is simple, if you know how to install windows then use you knowledge if not look for alienware youtube channel. actually the method 4 it told was alos from the alienware youtube channel so just look for that one too if you lost.

5. install all drivers for you computer before updating your windows. so make sure to download all the important drivers for you system from dell.com/support

6. your done. the link for Microsoft cd is at the bottom. :)  enjoy!!! your new SSD speed

A clean installation of windows might take more steps however this video will guide you on how to do it, yet you will need the windows CD or USB, you can try to request it here or you can contact the technical support site in your country to see if they can send it to you.