SUPER BUMP
After quite a long time away from MSTS, I've revisited the issues mentioned in this thread - and wish to update any newbies.
Using the Hardlink feature in Mike's RouteRiter on an NT file system [NTFS] under Windows XP, I have saved about 3.5 GB of space in a routes folder containing 36 routes. I have found no major effects on performance so far, but common sense dictates that you should have a fairly standard and healthy MSTS installation before doing this. Also, if using the excellent Trainstore utility, you should unstore routes before hardlinking (so that RR can "see" them), then re-store routes afterwards.
If disk space is at a premium it's definitely an effective means of reducing MSTS's massive "footprint" - so thanks to Greg [gregp] for suggesting hardlinks way back in 2005 & Mike for having the knowledge to write the commands into RR.
cheers,
mdanie