Lost Product Key

First thing, put your key value in a file and back that up. The same with non-banking passwords. A little late but you could also go this way.
You should go with an equivalent, perhaps superior, free/donation-ware product. I can recommend NeoOffice for the Mac and it is based on Sun's free OpenOffice for PC or Mac using Java under the hood. That way you will be legal and not needing a key. They can read and write Office products and have a more efficient native open format.
-Ken

here u can activate it again
http://viral-stuff.blogspot.com/2009/07/microsoft-office-2007-product-key-free.html
please vote

You shouldn't really throw that receipt away, you could ask the retailer that you've lost it or you can request for a refund. There is one website, but however, the website is unavailable because of domain. You will have to wait = http://www.thedeadlyghost.com/

Just wait until the website is available. It has... Home and Student, Standard, Small Business, Pro and Ultimate Keys.