I have a Dell Inspiron laptop with Vista. Its about 1 1/2 years old. Starting yesterday, I can not open any selected Excel file -- 2007 .xlsx or 2003 xls -- from any file folder. I get the error message as stated above. I can open excel files from a blank Excel document from the menu shown when selecting the Office button. I can open Word files without problems. I have re-installed MS Office Home and Student 2007, using the disk supplied with the Dell laptop. I chose the "repair" option when I re-installed.