I have Trainz 2009, I realize that 2G is the max for the archive, how can you save or archive routes that are say 4 or even 5G? it comes up in archive, splitting file, but still only archives 2G.
The 2GB limit is the limit of the archiving program libraries - a WinZip file process, which at the time of TS2009 was only 32-bits. It's no use trying to write something bigger because there's the off chance, well more of a chance of corrupting the archive and losing everything.
You maybe better off using CDPs, though they are even smaller than that.
What are you trying to backup/archive anyway? If it's your whole Trainz TS2009 install, you are better off getting one of those inexpensive external hard drives and copying the complete install to that. If this is for a route or two, the cdp files will work okay as well. The route and session can be packed into one and the dependencies spread over two or three for each route could be used for the content.