Here's the main files that're known working form my install.http://www.filedropper.com/tachreplacement
You can drop this on top of the install directory and overwrite, or copy everything you've got to a duplicate folder, then drop these on top.
Really Tachyon.exe doesn't do much... you can bypass it entirely and just add lines to a text file.
That file is in this set, but it's going to be set to my default video drivers.
But try overwriting with this, see if you can't run Tachyon.exe then. Or try launching Space.exe directly too.
*scratches chin* There's a couple other things it might be... but we'll start here.
You can get me over IM if you need to, I'll drop in the freespace and fringespace IRC rooms for today in case you want to directly get me.