How can I get muti-line tooltips?

If you are using version 4.70 or later of the common controls dll (comctrl32.dll), you can use the TTM_SETMAXTIPWIDTH message to force the tooltip control to display multiple lines.

In some cases, it's also possible to create your own tooltip window class, not based on the common control, and use that instead. This is specially useful for using it in your own custom windows, and it's relatively easy to accomplish, specially if MFC is involved.

A variation of this question is how to get muti-line tooltips for tray icons. Unfortunately, the answer is that it's not possible, at least not with the shell's tray support for tooltips. This is because your app doesn't own the tooltip window, as it's own directly by the shell. 

References and samples:

• Question 14 on this FAQ: "How can I redistribute comctrl32.dll?"