why can't I read .mht documents with my Ubuntu 10.04 LTS, recently installed?

Good Sunday,
I have a mini computer I received as a gift, about 14 months ago, and I recently updated to Ubuntu 10.04 LTS.
When I try reading an .mht document (as opposed to an htm or an html document), I am given the options of: Run in Terminal, Display, Cancel and Run, in that order, from left to right.
However, no matter which option I choose, the best that happens is that it opens the document, but it is all in what amounts to gibberish.
Is there anything I can do with this computer to make .mht documents decipherable?
Thank you very much!
Eliot.