Fix "Missing Event Receivers" issue in SharePoint Migration

During SharePoint 2010 Migration, Preupgradecheck reported the issue of missing Event Receivers:
The following event receiver assembly(s) are referenced by the content, but they are not installed on the web server

So,  To resolve this issue we need to two steps:

1. Get all list locations, where a particular event receivers  is registered
2. Un-register the event receiver from the list/document library.

Step 1: Get the list of location (Lists, Document Libraries) where the particular Event handler is registered:

How to get the locations where event receivers are installed? Simple! Just execute the following STSADM command:

 stsadm -o enumallwebs -includeeventreceivers > EventReceivers.txt

Now we got the report. By opening the EventReceivers.txt in Excel, you can examine where that particular event receiver is in use.

Step 2: Un-Register the Event Receivers:

We have got the locations now. Next step is un-register them. Here comes the Handy tool: Event Receiver Manager, download it from: http://www.ackermantech.com/utilities/EventHandlerManager.zip.

Navigate to the site from the report, Select the library, and then click "Remove Selected Event Handler" button. That's all!

Another nice utility to help on this issue is: SharePoint Manager http://spm.codeplex.com/ 

You can use:  Event Receiver Manager also. http://speventreceiverman.codeplex.com/