MS Excel 2007 is not responding

Hello,
Does anyone know why MS Excel is not responding when I open a file? The file contains 12 worksheets which I need to submit on Monday. I restart my computer and re-opened the file but it keeps saying " MS Excel is not responding". I also scan my computer and run virus check but still won't work. But the other files is working when I opened them. The most important file which I needed is the one that can't open and not responding. Please help. I need to get this done before Monday. Thanks a lot.
Rose
