Registry or GPO to MHT files

[imunro01]

I'm trying to find a way to configure Windows 7 to force MHT files to open in Google Chrome.

 

I've tried setting a file association in GPP and also tried to set it in Filexts under the explorer section of HKCU however it seems that Windows does not like the association changed on this.

 

Obviously I need this to apply to all users, so changing it on a per user basis is not an option

 

This is getting a little desperate now, so any help would be appreciated