Alot of games these days are dounloaded and you may never get a disk copy. Redunancy in storeage becomes inportant. Raid fore the games also can be fastert to load and run.
Os WIN 7 is expensive and if it curupts or gets degraded it is expensive to buy again and agian. It also runs better in Raid and loads and runs quicker if it is on a SSD.
Use ATCI if your moutherboard suports it as your file system type in a new build this alows TRIM to be enaabled in WIN 7. This is very important to Keep SSD's from curupting or even failing.
You are giong to want to Image boath the OS and your games in case of problems hence lots of disk space.
the internet where you play on line games is a danger also