An inexpensive memory stick can cost @ $20 USD and hold @ 8GB or more ... a DVD+RW disc (Re-Writable) holds 4.6GB, a double layer DVD+RW holds twice that ... an external hard drive holds 2TB or mor for @ $90 USD.
I copy my "Local" file and put it on and External HD for my TRS2006 ... Your version of Trainz maybe another file to copy to the External HD.
All your custom routes can be copied and saved to a memory stick, DVD+RW, or External HD.
All your payware assets & downloaded CDP's & Error Fixed CDP's can be put on a stack of DVD+RW discs, or an External HD ... in case of total PC failure or re-installation.
Sometimes Trainz acts choppy if you have a million billion trillion assets downloaded.