When I try to create a Excel 2007 Workbook project, in Visual Studio 2008, I get the following errormessage:
Project cannot be created because the \"Excel
I'd set Excel 2003 to open XLS files by default. I saw the same error message you got until I repaired Office 2007 from the Add/Remove Programs menu.
Just in case you haven't checked the trust settings, this MSDN page describes how to.
I came across this on a MSDN forum:
For the repair to work, you'll have to run the VS Command Prompt with Admin Priviledges (right click, run as administrator). Then run this command line:
C:>AddinUtil -AddInRoot:"%CommonProgramFiles%\Microsoft Shared\VSTA\AppInfoDocument" -Rebuild
If it still doesn't work, you may also have a corrupt pipleline store, which can be fixed like this:
C:>AddinUtil -PipelineRoot:"%CommonProgramFiles%\Microsoft Shared\VSTA\Pipeline" -Rebuild
You'll get one warning from that command but that is expected.
Failing that, I think you will have to run a repair on the Visual Studio 2008 installation (put the installation DVD in a drive, and select the repair option).