Is your production server part of a domain? IS your test server part of the same domain?

What user installed the express instance on the test machine, the local administrator or a domain user?

Same question for production.

Are you logging in as the local administrator or using your domain credentials?

When the Express instance was installed, did you download the installer from MS or was it part of a packaged product like Visual Studio or Sharepoint or some other such app?

Are you using the 32 bit versions of both products?

Also, are you trying to install a lower version like SQL Server Std RTM on top of Express SP3? That may also cause some issues, although I would think you'd get different error messages.

Another thing to look out for is SQL Server Manangement Studio Express. It can't be installed with the full blown SSMS that comes with SQL Standard.

-Luke.