Are you a Volume License customer, looking to migrate out of EBS per Microsoft's offer? Here are the part numbers you'll need to order the new media. Microsoft says to order from your original reseller. If you have EBS Premium, your SQL media will already work, so they have not included that SKU.
Windows Server Standard 2008 P73-03830
Windows Server Standard 2008R P73-04819
Exchange Standard 2007 312-03748
System Center Essentials 2007 UCH-01603 System Center Essentials 2010 UCH-02057