PNotes (Portable Notes or Pinned Notes) is written entirely in C and Windows API - so it is light-weight and fast. It is a free and open source note scheduling application that's light on system resources and well-designed.
Here are some screenshots to illustrate the features and user interface of this application:
Microsoft OneNote
Efficient Lady's Organizer Free
EverNote
QOwnNotes
C-Organizer Lite