We still use Office 2000, I've installed the 2007 compatibility pack to open .docx files but it doesn't seem to want to open .xlsx files, any ideas?

This is what MS say about it:

http://support.microsoft.com/kb/924074

What exactly are you doing to open the files? What happens when you try it?

Please be more specific when you say "doesn't want to open" the XLSX files.

Do you mean:

- When you see an XLSX file in Windows Explorer and you double-click on it, Excel doesn't launch?

- When you try open an XLSX file from within Excel, the file-open dialog box hides files with an XLSX extension so you can't see them?

- When you finally get Excel to try open the file, the file begins to open but then fails somehow, perhaps with an error message?

The first two are easy to fix, the third one, we'd need to know the exact failure mode and the details of any error messages.