SharePoint 2010 Server comes in only one edition (I’m not speaking of SharePoint Foundation 2010). There is however a confusion about Standard and Enterprise Editions, as if they were two quite different server editions. They are not, though Microsoft add to the confusion by making two separate downloads available on their volume license download site, VLSC. Ironically, the two separate download options are apparently designed to avoid confusion. Nevertheless the download pages confirm that whichever option you choose you will get the same bits: SharePoint Server 2010 64bit (for Standard/Enterprise) English Part Number X16-43564 File size 722MB Format ISO.
This applies to the volume license options for SharePoint 2010 Server, Standard & Enterprise, For Internet Sites Standard, For Internet Sites Enterprise. In every case you will get the same download bits.
The main reason for this is that differences between Standard & Enterprise levels are licensed per client in the case of SharePoint 2010 for corporate intranets, though there is additional confusion in that SharePoint for Internet Sites is licensed either as a Standard or Enterprise Edition. Again this is a licensing distinction not a technical one. So where’s the key?…
Although the SharePoint 2010 Server is the same download for Standard & Enterprise, and For Internet Sites Standard & Enterprise, the client differentiation is implemented by means of the Setup Key. This is hidden in plain sight on the download page. Many users, expecting to see it posted with their Volume License Keys, miss it altogether in their haste to download the bits.
Each Setup Key will affect the server installation in such a way as to provision that server with the chosen client functionality: Standard, if Standard CAL license has been purchased, Enterprise, only if Standard and Enterprise CALs have been purchased. Notice that the Enterprise CAL does not include the Standard CAL; it requires the Standard CAL, so to use the Enterprise Setup Key when you have only licensed Standard CAL would render your network uncompliant.
Worse still, if you inadvertently use the Enterprise Setup Key on install you will not be able to step down to the Standard Client level at a later stage without re-installing the server. However, if you use the Standard Setup Key on first install you will later be able to add Enterprise client functionality (for licensed users!) by entering the Enterprise Setup Key.