Add Log In Boxes at Checkout
 

I know this has been covered but I can't find it again.

Instead of having this text at checkout:

If you already have an account, please login from here. If you are a new customer we need to know your personal details. Please fill in the form below and click 'Submit'.

I would like to add the login username and password boxes. Please advise or point to a forum link.

Thanks,
Brian