Data Assistant was something Microsoft provided for PowerPoint 2003 users so that they could insert and manage graphical data objects such as Visio drawings, and Excel charts and named ranges into PowerPoint presentations. They stopped providing the Data Assistant, and I'm guessing this has not been updated for PowerPoint 2007 -- you'll need to disable it.
In PowerPoint 2007, choose Office Button | PowerPoint Options, to bring up a dialog box of the same name. Click the Add-ins tab in the list on the left, and you'll find the Manage Add-ins dropdown box right at the bottom. Select both Add-ins and COM Add-ins, and disable any entries that look like Data Assistant.
You can also remove Data Assistant altogether from your computer:
- Click the Start button in Windows, choose Control Panel, and then select the Add or Remove Programs option.
- In the list of currently installed programs, click Microsoft Data Assistant 1.0, and then click Remove.
- Follow the instructions to remove Microsoft Data Assistant 1.0 altogether.