I promised an update on SQL Express availability in my last post about the release of SQL Server 2008 so here it is. SQL Server 2008 Express is now available along with the release of the .NET Framework 3.5 SP1, which is a prerequisite and Visual Studio Express SP1. As I mentioned, there are two more editions of SQL Express on the way. There are a number of prerequisites for SQL Server 2008 that you will have to install on your own before installing SQL Express. Here is the list and basic instructions:
Windows Installer 4.5 requires a reboot on almost every system out there and SQL Express will fail if there are any pending reboots on the system so I suggested doing the following:
A note about Visual Studio Express SP1
Visual Studio 2008 Express SP1 includes the installation of SQL Express 2008; if you have an earlier version of SQL Express on your computer you will be offered the option to upgrade to SQL Express 2008. There are a couple cases where this offered upgrade will fail that you should be aware of:
SQL Server PowerShell is an option component in SQL Express 2008. Optional in this case means that we do not make Windows PowerShell 1.0 a prerequisite for SQL Express 2008, but it is required to use the new SQL PowerShell scripting. If you're interested in playing with SQL Server PowerShell, you should install Windows PowerShell 1.0 before you install SQL Express for it to work correctly. You can find the correct PowerShell installer from this page. If you have already installed SQL Express and still want to play with PowerShell, you'll need to repair you installation of SQL Express after you've installed PowerShell. In order to repair SQL Express you'll need to download it again (unless you happened to save your installer files) and select Repair when you see the Installation Center.
If you have the February CTP (this is the one that was installed by Visual Studio Express 2008 SP1 Beta) or the Release Candidate of SQL Express, you should be able to do an in place upgrade to the final release, no uninstall required. When the Installation Center opens up, choose the option to upgrade from either SQL 2000 or SQL 2005. I know you're upgrading from a 2008 version and it doesn't say that, but trust me, that is the correct path to follow. You will still need to apply the prerequisites before performing this upgrade.
If you have the November CTP of SQL Express, you will need to remove that before upgrading to the final release.
Upgrade & Architecture
With SQL Server 2008 we are releasing a 64bit version of SQL Express for the first time. SQL Express doesn't support cross-architecture, in-place upgrade, meaning you can't upgrade a 32bit copy of SQL Express to the 64bit copy. The only way to do this upgrade is side by side. You will need to either remove the old 32-bit version if you want to preserve your instance name, or you can install the 64bit version to a new instance name. We do still support 32bit to 32bit upgrade and we do still have a WoW enabled copy of SQL Express available from the download center.