The 650 is enough to run a game like vindictus and run it well, not sure if it will max it though.
If you are building a new rig then you will need an OS, if you are buying a pre-built one then they usually come with an OS unless otherwise stated. If you are upgrading an old rig then use the OS key from that and tell MSoft you replaced the mobo.
How are you sur it will not max out? i thought it was perfect, perfect to be maxed out ;x