Well, my experience for just “changing” the license key from Standard to Enterprise edition was not really that easy. First of all the textbox where you enter the license keys is grayed out. If this textbox is grayed out, how are we supposed to upgrade?

Any way, got around the problem by going to Central Administration –> Upgrade and Migration –> Enable enterprise feature and then select enterprise edition. This will allow you to enter the license key for SP 2010.

Remember to download and install the CU updates. For latest CU update for SharePoint 2010, please go here.

http://technet.microsoft.com/en-us/sharepoint/ff800847.aspx

Once CU updates are installed, remember to run the Configuration wizard. If you prefer to do the hard-way, you can skip running the configuration wizard and add each service application manually.

But while trying to create a new secure token (Requires  a key), you may see the following error.

“An error occurred during the "Generate Key" process. Please try again or contact your administrator. "

The error simply means that

a) Either you have not rebooted since you installed the CU updates

b) The id that you are running under does not have permissions to generate the pass phrase encryption keys and lastly

c) The managed service account that is running the secure store service has read/write access to the secure store service database.

For me, the last one “c” was the problem and once I granted SP_APP_SERVICE account the desired permissions, it was fixed.

That’s it.