I'm with Anne on this one. The various Auto routines are really only included for backwards compatability (that said, there have been rare instances where they work when the 'new' version doesn't ).

For Chip Pearson's take on the position have a look at the article here:
http://www.cpearson.com/excel/events.htm

For those who don't wish to read the whole thing, the relevant part is ...
Event Procedures And Auto_ Macros And On? Macros

If you have programmed in previous versions of Excel, you are probably familiar with the Auto_Open and Auto_Close macros, which execute when the workbook is opened or closed, and with the OnEntry and OnSheetActivate properties, which execute when you enter a cell or worksheet. While these macros are still supported in Excel97, for compatibility with workbooks created in previous version, they have been replaced by event procedures.

In general, you should not use the Auto_Open and Auto_Close macros in new workbooks. While they will still work as expected, you should become familiar with and learn to use the new event procedures. Of course, if you are developing a workbook that will be used by users with an earlier version of Excel, you cannot use event procedures and must use the Auto_Open and Auto_Close macros. Remember that when you open a workbook through VBA (with the Workbooks.Open method), the Auto_Open macro is not executed. You will have to use the RunAutoMacros method of the Workbook object to run it.