I use two programs at the moment. Milkshake to convert the MOD to Light Wave 6, then Ultimate Unwrap 3d to convert the files from Light wave 6 to X format. I paid for Unwrap 3d but am having issues with it not opening MOD files like it did before I purchased it. Otherwise I would just be using Unwrap3d to do the whole process. Its really an inexpensive program at only $50.00 US.
By convert I mean Import / Export.
(There are many files that Milkshape cannot open and often will crash when trying.)