Saboo

I want to change the defaults so when I open multiple spreadsheets/workbooks
they open in one application of excel only - i.e. if I go to 'View -> Switch
window' all the workbooks are shown.

Currently when I open an Excel file it will open automatically in a new
instance of Excel. I know I can open mutiple files if I choose 'Office
Button -> Open' but if I double click an Excel file in windows explorer this
is when they open in a new application of Excel.

I know you can do this in previous versions of Excel but cant find this
option in Excel 2007.

Can anyone offer any advice please?