Download Windows 7 OEM

Hi

I need to create a bootable usb with win7 on my new E5450.
I saw a recent post which lead me to:
http://www.dell.com/support/home/us/en/19/Drivers/OSISO

1. Will I be able to make a clean install of win7 on my Latitude E5450 with this iso?
2. What do I need before reinstalling win7?
     Windows 7 Product Id etc? Anything else?
3. Why do dell install win7 on my machine and then deliver win8 on dvd when it comes without optical media player?

Thanks