Well,
http://www.techbargains.com/, is a great place to find the cupons. Today they found Dell offering:
Dell Home $750 off $1499 Select Inspiron Notebooks, Jun 7
Which is already expired, which sucks.
They don't last long. Today's expired Friday or 15,00 uses. Whichever came first. I'd bet your cupon expried. It's not the kind of thing you can keep until you're good and ready to use it.
Better luck in a few weeks.