I am having a similar problem, however, I am the administrator. Last month I had to uninstall and reinstall Office 2003 Basic. After that the converter to convert .xlsx files to .xls quit working. I have uninstalled and reinstalled every which way possible and have reinstalled all the updates and I continue to get the same message when I try to reinstall FileFormatConverters.exe. "Another version of this product is already installed. Installation of this version cannot continue. To configure or remove the existing version of this product, use Add/Remove programs on the Control Panel.
Compatibility Pack for the 2007 Office system (FileFormatConverters.exe)
The Installation of this package failed."

I cannot remove the former version from the control as it is NOT listed there. I have searched and wasted probably 15 hours trying to find what is on my HD that is causing this. Why Microsoft blocks the ability to reinstall over an existing install is beyond my understanding. Can anybody help? I've found that I am not the only person with this problem. But I cannot find the solution anywhere. I even found the question at support.microsoft.com BUT there was no solution offered.

Thanks