Sheldon,
I have a Mac computer and open, edit and play the midis from MidiSwing, a free App (which I'm told may not work as well on PC). It should work perfectly on your old Pro Laptop. A USB to midi cable connects my computer to the piano. I edit files 'live' thru the piano. All my files work perfectly thru the DKC-850 of a friend.
I find MidiSwing intuitive and simple to use with great flexibility. It is quite indispensable, although I do use it in occasional conjunction with Zenph RePerform and a couple of other freely available apps to achieve all I need to manipulate midis.
I am able to convert Type 1 midis to Type 0 and to quickly adjust note velocities throughout an entire midi to optimise the reproduction thru my Enspire piano, as the original unaltered midis would otherwise play back far too loudly. MidiSwing also permits me to edit sustain pedal, correct wrong notes and adjust tempi throughout. In fact, I am now able to successfully emulate favourite performances of piano works I have on CD, simply by manipulating these parameters, bar by bar through the entire piece.
The virtual piano roll interface is very useful in identifying and correcting notes of extreme velocities, because the notes appear on screen as the perforations in the original roll, all coloured blue –– light blue for softer and darker, or more intense blue for louder sounding notes.
Send me your email address as I have written out full instructions for using MidiSwing.
Ian