For excel, you have the PERSONAL.XLS file to store macros to be readily available.

If you don't have a personal.xls file, it is easy to make one. From excel, go to Tools, then Macro, then Record New Macro. On the 'Record Macro' window, change the "Store macro in" to 'Personal Macro Workbook', click ok, then click the Stop Recording button. Go to your VBA editor, and you should now see the VBAproject for personal.xls, with a blank recorded macro in Module1.

What that does is create a new workbook in your xlstart folder named 'personal.xls', which is set to be hidden. When excel starts, it will also start your hidden personal.xls file, which contains your macros. You can create this yourself there, or just record a new macro as specified above, and you'll have the file available now.

I can't help you with powerpoint, unfortunately. I never use it, so am not sure of how it works there.

Matt