After Steam finishes installing Railworks, it's quite easy to create a restorable backup.

From the "My Games" list, right click Railworks and you'll be presented with a menu. Select "Backup game files..." and you will se a list of all installed programs that Steam has installed. Railworks will probably already be selected. If that's all you want to backup, click "Next" and decide if the default location is ok. Another "Next" and you get to decide if you want to create an archive that would fit CD's or DVD's. The next "Next" starts the backup.

When it's completed you can now write a CD or DVD set that when autorun will restore the backup. I haven't tested this part myself but the file structure created looks like that's the way it will work.

I'd say Steam has made backing up and creating a restorable version quite painless. I did just fire up the restore (but didn't restore). It appears that it is an all or none restore rather than a fix one bad file restore.

Hint.. This doesn't mean that you couldn't do a complete Steam directory backup which would include all directories and files. All the Railworks files would then be accessable with a bit of searching.