Where are system notifications in KDE4?
 

KDE3 had in System Notifications a section for KDE System Notifications, where there were settings for critical message, question, startup, etc.

In KDE4, that category seems to not be in System Notification Configuration. Where to I find those settings - sounds for errors, startup, etc.?

Do you mean System Settings > Application and System Notifications ?

My bad, did not look hard enough. KDE4 calls it KWin Window Manager....

Select Common Appearance and Behavior
Select Application and System Notifications
Select Manage Notifications
In the Event source drop down list, select KDE Workspace