Reading it again, setting FEATURE_MIME_HANDLING in the registry will only activate Microsoft's additional MIME checking they introduced in SP2 for your application, sorry. :sigh: I think to actually handle a particular MIME type at runtime you might need something like http://msdn.microsoft.com/library/default.asp?url=/workshop/networking/pluggable/reference/ifaces/iinternetsession/registermimefilter.asp[^], though I don't know enough about it at this stage to give you an example. This is something I might need to use in the coming months so if you make any progress it would interesting to hear how you get on. :) mitooki