If you've got either Excel 2003 or Excel 2007 on your machine, then you shouldn't need to download anything. You just need to add a reference to the Microsoft Excel Object Library under the COM tab to your project - it should be version 11.0 or 12.0 - and Visual Studio will do the rest.
However, I would add this line to your using directives:
using Excel = Microsoft.Office.Interop.Excel;
If you'e still using Excel XP, then you probably will need to download the XP Primary Interop Assemblies from <a target="_new" href="http://www.microsoft.com/downloads/details.aspx?FamilyId=C41BD61E-3060-4F71-A6B4-01FEBA508E52&displaylang=en">here</a> before you can add a reference to the Excel object library.

Vulpes,
I've got Excel 2003 and Excel 2007 on my machine. I'm using C# express edition. If i want to add the Microsoft.Office.Excel reference from COM, i can't find that in the list.
any ideas?
tx!
david

I've got Excel 2003 and VC# 2008 Express on the machine I'm using just now and the reference is called the Microsoft Excel 11.0 Object library under the COM tab.
This should have been installed with the product.
If you still can't find it, can you let me know the link from which you downloaded what you've been trying to use.

this is the link http://www.pcrepaircentral.com/dlldownload_20813.html
at the middle of the page is this button
Download office.dll <download>
In my list i don't have the reference called Microsoft Excel 11.0 Object
sorry
david

Try this 'official' download for the Office 2003 PIAs instead:
<a target="_new" href="http://www.microsoft.com/DOWNLOADS/details.aspx?familyid=3C9A983A-AC14-4125-8BA0-D36D67E0F4AD&displaylang=en">http://www.microsoft.com/DOWNLOADS/details.aspx?familyid=3C9A983A-AC14-4125-8BA0-D36D67E0F4AD&displaylang=en</a>
There's also a link to the Office 2007 PIAs as well towards the end of the page.

thanks vulpes
I apreciate your help!