This is a well known issue with Office 2007 and Vista. Would be helpful to know what version. Generally worse with Vista Home or Home Premium. Hopefully, you are using Business anyway.

This issue is usually due to a problem with the MSI which currently is called Windows Installer. One problem can be added programs which use WISE or Wise Installation which may not play well with MSI. There are a number of ways to fix this issue, one of which worked for me when I had the problem.

Cleanup Utility

http://support.microsoft.com/kb/290301

Try installing this little utility to remove the installation file associated with the program. If AC is in the list, uninstall installer. Don't forget the Sentinel System Driver is Amazing Chart's. If those aren't there or aren't helpful, use it with 2007 although Microsoft doesn't advise it. This tool is VERY helpful.

Second, try

Downloading and installing Service Pack 1 for Office 2007. May want to thy this first as you will find it helpful either way.

http://tinyurl.com/3xxf6l

SP1

Lastly, and especially for Vista users, try David Overton's site:

http://tinyurl.com/3adbbm

hth

Bert
Pediatrics
Brewer, Maine