OK, what you have there, is part 1 of a multi-part archive. You will need to download that, as well as all other parts in the archive - they should be named '1840_2000.part2.rar' through to '1840_2000.partx.rar', where x is the number of the last part (if you don't know how many parts there are, a clue should be in the size of the files - they should all be approximately the same size, except for the last, which is usually smaller).
Once you have all the parts in the same folder, them run a utility/app called 'unrar' to unpack the archive (you may have to install this) - the resultant file(s) may already be mp4, or other video format (avi, mov, mkv, divx/xvid for example).
Hope this helps.
-G.x
Lexi Lowe? Sorry no, she's not someone I'm familiar with, I'm afraid ...
Good luck in your quest ...
-G.