Jay,

I say there is probably something going on here with servicepack levels. The Express edition that you downloaded is most likely at SP3 if it was downloaded recently. Unless you have the standard edition that is bundled with SP3 it might be trying to go backwards then forwards although I would think that would cause a different error message.

I'm somewhat and the end of my rope on suggestions beyond that, but I think that this might be a covered issue with MS PSS (MS Product Support Service).

I might suggest another option that may/may not work for you depending on how your application is configured. I might look to do this as a side by side migration. Basically you install the Standard Edition on the same box to a different instance. Then you can script out your users/logins and such add them to the new instance, Once you verify that everything is exactly the same, you can detach the database from the express instance and re-attach it to eh Standard edition instance.

The only drawback to the above is that your instance name will change, which if Express was installed in it's default configuration is called SQLExpress so you might want to change it anyhow, but that all depends on how easy it will be to change your connections in your application(s).

-Luke.