In Microsoft Dynamics CRM 2011 you can export data to edit in Excel and then import the data back to CRM.
To do this, you select the Make this data available for re-importing by including required column headings option.
The export file has a .xml extension. To edit the file you must open it with Excel, however if you get a message that the file is corrupt it may be that you need to unblock access to the file. Right-click the file and on the General tab click the Unblock button.
To avoid this add the URL for your CRM installation to the Trusted Sites zone of Internet Explorer.