For those how would like to try Windows Server 2008 R2 Foundation Operation System with Backup Exec Windows licenses, this might be information. :D
Windows Server 2008 R2 Foundation is a new server OS from Windows. This is “smaller” (less functionalities) than a Small Business Server.
This Operative System includes a Windows File Server and Active Directory. Customers with this type of servers who would like to have backup copies would need to have a BE for Windows Standard as core license. Small Business Server key will NOT WORK, in Windows Server 2008 R2 Foundation.
For customers with the wrong product, they may need to contact their direct reseller to request for exchanging product. However, make sure to check the purchased date. You may return or exchange it within 45 days only. Else, it would be the reseller's choise if they will let you have the product you need.
Additional information about Windows Server 2008 R2 Foundation can be found in the link below.