Excel 2003 slow closing files in Vista SP1

[Sunny]

I have a spreadsheet with macros that is ~1.5MB in size. In Windows XP (on
two different computers) if I close Excel (x-button), select "save file
before close", it takes ~2 seconds and the application is closed.

In Vista (home premium, new Lenovo notebook), it takes ~6 seconds to do the
same. Are there any settings in Excel that I can change to speed this up?
Or, is this a Windows Vista issue?

Both are running Excel 2003

Thanks