OSD with C#

First of all, what is an OSD? OSD is a short text message, displayed to the user when some event occurs – like the user presses the key, file downloading is complete, a new mail has arrived, and so on. An OSD (and OW, obviously) must possess three main characteristics:

* Should always be the top most window: User must see our message even if he/she is working in Word, IE, or reading a mail.
* Should always be completely transparent: User must see the text, and not the background of OW.
* Should always be completely transparent to mouse/keyboard events: This means that the user must be able to select an icon positioned "under" OW through OW. Or, if the user is working in Word, and OSD's text is displayed "above" Word's main area and the user moves the mouse pointer in OSD's client area, then the mouse pointer must not change its appearance to "Arrow". Instead, it must keep the "Text select" form. In other words, the mouse/keyboard doesn't "see" OW, but the user does. :) Needless to say, OW must be transparent to the system as a whole – no button on the task bar, no entry in Task Manager, etc.

The suggested solution completely fulfills all the three requirements. Moreover, it offers additional features (optional, of course) – a bunch of animation effects when OW is shown/hidden, the OSD text itself may be fully opaque, fully transparent, or in between, and some others.
Code project link