I am a big fan of TooltipFixer which fixes a Windows shell bug where tooltips in the notification area would be eclipsed by the taskbar itself.
In Windows 2003, the service would have problems at startup and trigger the annoying and unhelpful: "At least one service or driver has failed to start" error dialog. This can be fixed by adjusting the properties of the NST ToolTipFixer service to log on as "Local Service" rather than "Local System".
