Here's a link about it.
by R. Proffitt - 11/26/12 8:43 AM
In Reply to: What is MHTML? It's use by CNET is preventing downloads by amnot
I've seen downloads that have .MHT files. These are all over the map as to what they contain so I can't offer anything specific except Microsoft seems to be dropping support for it.
There should be many downloads out there containing or being just a MHT and since no one is actively converting these to something else, you have a choice to make. Ignore the download or research how to add support for it to your choice of OS.