RadSpell for ASP.NET AJAX control still does not support MS Word spellchecking, due to interoperability
problems with the MsWordAdapter.dll. The problem is already logged in our bug tracking
system and we will try to implement this feature for the next update of RadControls for ASP.NET AJAX.
As a side note, you should be aware that MS Word spellchecking uses
significant amount of server resources and if a lot of users spellcheck
their documents at the same time, this could considerably slow down
your server. That is why my suggestion is to choose one of the other
spellcheck algorithms SpellCheckProvider="EditDistanceProvider" or
SpellCheckProvider="PhoneticProvider". The PhoneticProvider is
convenient for the English, German and French dictionaries.
the Telerik team