There is a program called RRTrains 2000 that is similar to a spreadsheet, but is setup and ready to go. I have looked at it and it doesn't look too bad. I can't remember for sure, but it might possibly be Freeware?
There was another one I looked at a few years ago called Yard Boss or Yard Master or something like that? It looked pretty good as well, but just wasn't quite enough lure me in.
I think both of the above might be worth a look though, just to see what you think of them. Something to look at anyway.
I use a Filemaker database, I customized one of their included databases that were pre-made. But, as many others have stated, I have fallen behind and it is really in need of an update! I have all my pre-orders entered, it's the off the shelf purchases I am really behind on and the ones I regularly forget to add.
I usually use a simple Excel SS for figuring out my pre-orders and give to my LHS for ordering. Then once they are ordered I put them in Filemaker. I could probably just use Filemaker, but I only list the needed info for my LHS to order them in the Excel SS.