Problems opening up excel ss in email - (use Lotus Notes - have Excel 2007).

Every time I "try" to open a ss from email - it goes into a download folder
and you have to do an annoying series of steps to get it to open- most of the
time the spreadsheet is blank and I get this error message: ..."xls could
not be opened, because the associated helper application does not exist.
Change the association in your preferences."

Please help!