Post-It Notes

Post-It Notes is a Windows application you can use to create sticky notes on your desktop to help you remember important tasks of events, such as buying groceries, attending a meeting, or working on a school project.
It gets integrated into the systray and gives you the possibility to add as many yellow notes as you want to the screen, as well as to schedule alarms.

Click the tray icon to create post-its

Once launched, the program creates an icon in the taskbar notifications area but doesn't signal its presence by showing a notification message or by bringing up a window to the screen.
You can click the tray icon for each new sticky note you want to add, then type or paste text. The title automatically changes to match the first line of text.
A note can be collapsed into a small bar by clicking the arrow on the upper-right corner. This way, you can tidy up the desktop and move the note anywhere to focus on other matters while still keeping an eye on them in Post-It Notes.

Set up alarms with messages, audio alerts, and app launches

By right-clicking a note's title bar, you can open a context menu to keep the note on top on other windows, reset it to its default position, close or delete it, as well as schedule an alarm to go off at a specific date and time. It can either display the post-in on the screen, pop up a message, play an audio file, open a file, or run an application when time's up.
By right-clicking Post-It Notes' icon in the systray, you can reset all notes to their original positions, keep them on top of other panels or restore the window state to normal, delete or close all notes, open all closed notes, or open a note by title.

Old but still operational on newer Windows versions

Unfortunately, the tool hasn't received updates for a very long time and doesn't seem to be in development anymore. It doesn't implement options for customizing the note font and colors, for example. However, it worked smoothly on Windows 10 in our tests.
Also, some antivirus engines might flag Post-It Notes as being infected but this is only due to the fact that the downloaded archive was packed by the developer using UPX. Our tests have shown that the program is, in fact, clean.
Furthermore, the shareware version can no longer be purchased but there are no limitations in the free version, so Post-It Notes can be used for free with all its features. It may seem rudimentary but it offers a simple solution for creating sticky notes with scheduled alarms.