I work in an IT Department and a user has come to me with this same problem.
Dell Latitude D600 laptop
Windows XP Professional (DELL OEM)
Windows XP Service Pack 2
Office 2000 Professional SR-1 (with SP2 and SP3)
Visio 2003 (classed as an Office 2003 installation)
Internet Explorer 6
I have tried looking in the Microsoft Knowledge Base but everything I have tried makes no difference. I have also repaired the installation.
If I type into the Office assistant search box (e.g. 'underline') I get some matches. If I select a match a help window appears but is blank (a light grey colour). I have the same result which ever version is being used (2000 or 2003).
Any help/suggestions would be very welcome as a reinstallation of the machine is "out of the question" to quote the user.
Thanks.