Office Customization not available

You can get this error when you are trying to load the template file.This is because of the following reasons :

1)Prerequisites needed for the template (Microsoft Primary Interop Assemblies,Visual Studio Tools for Office Second edition runtime,.Net Framework )
Here the version of .NET Framework has to be verified with the Excel version in use(C:\Program Files\Microsoft Office\OFFICE11\Excel1.1.exe ( xml config file depending on the .NET framework version ) )


2)Template is not having appropriate permissions ie., template (XLT file) is not having 'Full Trust' access rights.To gain full trust, you have to create a strong key and add that strong key to (C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\CONFIG\security.config) / (Control Panel -> Administrative Tools -> Microsoft .NET Framework 2.0 -> (Expand the tree).NET Framework 2.0 configuration ->My Computer -> Runtime security policy ->Machine ->Code Groups -> All code ).I prefer the latter one. This is because it is UI driven and required strong key can be easily added to it.