One of the powerful things about WSS / MOSS is editing list in datasheet view.   It’s like working with a spreadsheet except it’s on the site.   I recently got a new laptop and couldn’t do this.  The error listed below came up.

“The list cannot be displayed in Datasheet view for one or more of the following reasons: A datasheet component compatible with Windows SharePoint Services is not installed, your browser does not support ActiveX controls, or support for ActiveX controls is disabled. 

My laptop has IE 7.0, Windows XP, Office 2003 professional, OneNote 2007, Visio 2007.    I hadn’t tested this functionality before installing the 2007 products.   After I ran a repair on Office 2003, this resolved my issue.   Hope this helps others.

PS: Many posts mention upgrading to 2007 resolves the issue.   From what I can determine, the COM entries to this feature gets updated when installing 2007 based products while mixing with Office 2003.