two wordpress installs – one registration.

Hi,

I am in a situation where i need one wordpress install to act as my homepage. this is yoursite.com
And another one to host and secure my course content. this will be courses.yoursite.com

i need to set it up so that once they register on yoursite.com they are also registered with the same access rihts to courses.yoursite.com

Can you please explain how i would go about setting this up… is a multisite what i need?