Problem with Mail Merge to Microsoft Word 2007

Problem with Mail Merge to Microsoft Word 2007

When we try to create a mail merge template in Microsoft Word 2007 we get the following error....

See the end of this message for details on invoking 
just-in-time (JIT) debugging instead of this dialog box.

************** Exception Text **************
System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.Office.Interop.Word, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c' or one of its dependencies. The system cannot find the file specified.
File name: 'Microsoft.Office.Interop.Word, Version=14.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c'
   at ZohoCRMOfficePlugin.MergeForm.ButtonMerge_Click(Object sender, EventArgs e)

Any help appreciated.

Regards
Andrew
PDM