Have a used laptop excel asks for product key but i click cancel and have used the software but now it opens and i can't edit or do anything is there a way to fix it or is there a way to download another version and use it...the one i have is 2007

MS Excel is not afree program.
You will need to purchase a copy of MS Office which includes Excel.
For an alternative free program OPEN OFFICE is a full-featured officesuite that's compatible with Microsoft Office.
If you want Open Office you can download this free program.
Click on this link to download :-
http://www.openoffice.org/

Hey there,
Microsoft Excel allows users a trial period for use and asks the user to enter an activation key each time the program is opened. Once you pass that trial period (which it seems you have done), Excel will open but not allow you to actually use the program. You would need to purchase either a new excel program from Microsoft or contact Microsoft to receive an activation key.
Another option would be to trial the new office 2010. You can download excel 2010 here and have a 30 day trial period
http://office.microsoft.com/en-us/excel/
Hope this helps!!

You can download a trial of Office 2010, but Office is not a free software. You will have to buy it eventually. You could also use OpenOffice. It's an alternative to Office, including Excel! And it's free!