How can you make Excel 2007 stop formatting large numbers as scientific notation?

You can, but it takes a couple of manual steps. These steps are from Excel 2003, but I'd assume the wizard is similar in 2007:

1. Rename the file as TXT. Don't double-click it.
2. Open Excel
3. Click File, Open
4. Locate and double-click the text file
5. It should open a "Text Import Wizard"
6. In step one, choose "Delimited"
7. In step two, uncheck "tab" and check "comma"
8. In step three, scroll-over to the last column, shift-click to select all columns, then click "Text" as the format.
9. Ignore the annoying "Number stored as text" warnings everywhere

Goes pretty fast with some practice.