I have developed a number of PC applications, mostly for my own use, with the earliest production quality one that I still have dating back to around 1996.
Winsploin (1996 – 1998)
A Borland Delphi application that splits and joins large files over multiple volumes, making use of the sploiner tool which can be downloaded from here
I used this (prior to removable USB drives) to split large files onto multiple floppy disks for transportation!
The best feature about sploiner was the creation of the shadow file. Should one of the parts be damaged (as was often the case on floppies) you could use the shadow to regenerate it.
Midi Jukebox Player (1997)
Windows IR Listener (2003)
A visual basic (VB) developed application that I used to prolong the use of my Creative PC-DVD Remote, after the DVD drive died. This program listened on the serial port for remote control presses and could move the mouse, control programs, and even type, all via buttons on the remote.