This is a known issue in versions prior to 4.8. Upgrading to the latest version is the permanent fix. As a workaround, change how TaskCentre is launched so it looks for images in the correct folder:
Close the TaskCentre client.
Create a shortcut to TaskCentre on your desktop.
Right-click the shortcut and select **Properties**.
Set the **Start In** folder to c:\iwtemp.
Start TaskCentre using the shortcut.
TaskCentre should now correctly embed images in the HTML source.