Perhaps a call to Microsoft would help.
http://support.microsoft.com/Default.aspx
that's the general Microsoft products support portal page, and
http://support.microsoft.com/kb/811224
has info on contacting them for a replacement key.

Good luck.


"kiki2" wrote:

A month ago I downloaded Excel 2007's Trial Version...all OK. I previously
had Excel 2003 installed. I purchased an upgrade of Excel 2007, placed the
disk in the C drive and followed the installation instructions. (I should
have used the conversion route, but I didn't.) It appeared the upgrade
installation was successful, but the "Trial Version" notation still appears
on the top line of the screen. I then went the conversion route, entered the
Product Key again, and received the message something like "Product Key
already used." How do I make the Product Key work...or how do I obtain a new
Product Key? What to do, please? Thanks. Kiki2