I’m going to start out by saying that I strongly suggest that you should really go to http://www.microsoft.com/licensing/ for information. Anything I write about here is probably wrong or at least outdated. So please don’t listen to me. I have over the years called Microsoft directly asking the same questions about licensing and received different answers from each person that has helped me. Not to complain, just that it is a serious, important and complicated issue. My only goal here is to provide you with some basic information.

Of course you have the option to purchase licenses from whichever vendor you choose but you do have some options that will provide you with some additional benefits and flexibility.
Unless you are a large organization and if that is the case you have additional options to purchase licenses directly from Microsoft. You are probably going to use one of the following two options.
Open License which includes: Open License Value, Open License Volume, and Open License Business
Select License
And don’t forget about Software assurance.

First, is the Open License Value. This program has the following characteristics:
If you have as few as five desktops and want Software Assurance and wouldn’t mind the ability to spread your costs over annual payments this is a possible program for you.
Entry Minimum: 5 Licenses and Software Assurance
Software License Offerings: L&SA, and SA renewal
Additional Savings: Yes for company wide option.
Payment Options: Up front or annual
Term: 3 years
How to Acquire: Resellers
Product Media: Initial Media provided, subsequently trough fulfillment
Order Tracking: Microsoft assigns an agreement number and posts order confirmations on the MVLS website (in most countries).

Next is Open License Volume:
If you have a large up front purchase this my have benefits.
Entry Minimum: 500 points in initial order including OS, Servers, and applications.
Software License Offerings: License, SA, SA renewal
Additional Savings: None
Payment Options: None
Term: 2 years
How to Acquire: Resellers
Product Media: Fulfillment
Order Tracking: Microsoft assigns an authorization number and posts order confirmations on the eOpen website (where available) or sends an authorization number and physical order confirmations directly to the customer where eOpen is not available.

Next is Open License Business.
This might be the option for 5 or more licenses.
Entry Minimum: 5 OS licenses.
Software License Offerings: License, SA, SA renewal
Additional Savings: None
Payment Options: None
Term: 2 years
How to Acquire: Resellers
Product Media: Fulfillment
Order Tracking: Microsoft assigns an authorization number and posts order confirmations on the eOpen website (where available) or sends an authorization number and physical order confirmations directly to the customer where eOpen is not available.

Select Licensing:
If you have the ability to forcase the number of licences you will need for the next three years. You might qualify for the following benefits:
- Use Software Assurance. This allows some flexibility for home use and migration and upgrades.
Volume discounts based on your forecast.
- Ability to annualize License and Software Assurance costs over the length of the agreement term.
- Ability to obtain licenses through a worldwide reseller channel.
- Easier management of license portfolios with the MVLS website.