I saw this (How to buy Microsoft products) and thought I should share.  Not only does the site have some very simple information on what solution may well be right for each customer and how to choose, but if you are still confused there is a good questionnaire to help you and a link to find your local SBSC partner.

Find the right purchasing option for you

Volume Licensing Best option for companies that would like to save money on software by buying in bulk. If you are buying more than 5 licences for any mix of Microsoft products, you could save money in comparison to buying boxed software. Learn more Hosted software Best option for businesses that want to outsource IT. You can rent the right to use Microsoft products through an IT provider who offers Software as a Service (SaaS). Learn more Software in a box from a retailer Best option for companies that only need one or two copies of software, or that want the convenience of an instant purchase. You can buy software in a box that contains a licensed software CD for installation on a single computer. Learn more Pre-installed on a new computer Best option for companies with plans to buy new computers. If you are buying new computers for your company, you can have many Microsoft products pre-installed. Learn more

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David