First, we need to recognize that this can only occur on a Windows Server 2003 x64 installation, since upgrading from x86 to R2 is not a viable pathway.
I haven't specifically done an upgrade from Win2003 x64 to Win2008(R2), but a few months ago I did a test upgrade on a WSUS server environment for preparation on a deployment webcast. That upgrade was from Win2003 x86 to Win2008 SP2 x86. Generally I avoid Operating System upgrades like the plague, but I did this one to have appropriate informaton on a Go-NoGo decision for those who had no choice in the matter. I must say I was pleasantly surprised, and the upgrade executed flawlessly. The only downside I saw was that when upgrading an IIS machine, the IIS7 installation included ALL features/components, so some uninstallation of IIS7 features/components would be necessary as part of the post-upgrade installation, but that's not going to be an issue on an Extension Pack server, and it was only a minor annoyance on the WSUS server.
Based on that experience, I would be surprised if there were any particular issues doing the upgrade on an ExtPack server, or from Win2003 x64 to R2; however, falling back to my preferred methodologies... even though the upgrade works... I'd still be inclined to do a fresh installation of the OS, in preference to the upgrade, if it's an option. If moving from Win2003 x86 to Win2008 R2, this is the only option.
In those scenarios you'd want to do these steps to implement the 'migration':
1. Stop the EminentWare Data Grid Service on the existing server.
2. Detach the Extension Pack database from the installed instance of SQL Server Express Edition.
3. Copy the MDF and LDF files to a safe location.
4. Install a fresh Windows Server 2008 R2 installation.
5. Given that you're installing to 2008 R2, I would also recommend taking the opportunity to upgrade the database instance to SQL Server 2008 R2 Express Edition, so installing SQL2008 R2 Express would be the next step.
6. Reinstall a fresh Extension Pack.
7. Stop the EminentWare Data Grid service.
8. Detach the newly created (empty) Extension Pack database, and move the empty MDF and LDF files to a safe location.
9. Copy the original MDF and LDF files back to the new server.
10. (Re)attach the Extension Pack database and restart the EminentWare Data Grid service.
Of course, I also recommend testing this procedure on a TEST environment prior to a PRODUCTION environment, but this methodology should suffice to 'migrate' an Extension Pack server from a Win2003x64/SQL2005 environment to a Win2008R2/SQL2008 environment.
I'd allow about four hours of time for the procedure.
There is one extra consideration for this scenario that just occurred to me.
Because the new server will be installed with a new service account and password, all of the passwords for the stored credentails will need to be updated to use the new encryption keys, as they'll be based on the original account/password.
