Install MongoDB on Windows 8.1 64bit

i want learn mongodb, try to install mongodb on my windows 8.1 64bit,

open the official website, there are only for 2008

• Windows 64-bit 2008 R2+


• Windows 64-bit 2008 R2+ Legacy


• Windows 64-bit Legacy

My question :

1. What i must chose ?


2. Why there are no for like XP, Vista, 7, etc


3. What is Legacy ?

thanks, sorry for newbie question.