Pogmoor says :
I can't open these files; Finale 2009 says they have been created with a later version.
I really cannot told you about upgrading your 2009 edition to Finale 2012 for free. Try Finale team official site -maybe the upgrade is free.
Free upgrades? Updates yes but upgrades never (generally speaking). If they just gave away the new versions their would be no revenue to budget for development of new features/improvements. Upgrade for Finale runs a little over a hundred (perhaps more upgrading from a 4 year old version). As a general rule when buying audio production software it's going to cost about $100 every year or two to keep it current. But until compatibility becomes an issue (when collaborating, etc.) most hobbyists can get away with only upgrading every couple or few versions (skipping a version or two) or so before upgrading or not at all (although sometimes it costs a little more to upgrade older versions).
Another possibility (if exporting as xml doesn't work) is using a universal format. Print the sheet music in one program and use sheet music scanning feature to import into the other. Don't know how far along scanning sheet music has come but in the old days (a few years ago in computing) scanned pages needed a lot of touch up work (back then it probably would have been less work to just edit and fix the midi file).
BUT one more thing about MIDI: General midi should be cross compatible. Same note, same note durations, same instruments, etc. But one thing that will change are the ties, and voices for example. If you have a half note tied to another half note midi will only have one whole note and MIDI doesn't recognize different voices for the same instrument (it sees a bass line and melody line as part of the same voice unless each voice is assigned to a separate instance of the same instrument (in which case midi will see two independent lines altogether) . There are a few other things like this that get translated differently in MIDI but for the most part general midi is a universal language. The issues with exporting midi from one program and importing into another aren't questions of compatibility but rather limitations of MIDI itself and often more so, the limitations of the midi import feature on the software being used.
That said, there are two types of midi files (type 0 and type 1). One is compiled with all tracks and instruments crammed into a single track. This type is used for simple midi playback (good for ringtones for example) or for playing in the background situations but the other actually creates a separate track for each instrument and these are much easier to work with, edit, and for importing into other audio programs. Anyway you might try changing the type of midi file you are exporting to the other. They still might require some touch up work but I think that this might solve your problem. And finally another possibility is to export individual voices in the music and putting them back together.
One Ring to rule them all, One Ring to find them, One Ring to bring them all, and in the darkness bind them.