SQL Express refuses to install

I'm in the habit of removing any beta versions before I load any release versions, so I meticulously removed SQL2005 Express beta, Web developer Express beta, etc., and rolled back to a restore point set before any of the beta packages were loaded. Just to make extra sure, I rebooted the machine before beginning to download and install the released Express today.

I opted to install Web Developer complete with The 2.0 framework, SQL 2005 and MSDN in one go. The install plodded along, downloading the 200Mb of MSDN and 54Mb of SQL and then stepped through a bunch of installs. It reported no problems.

Imagine my surprise when the first starter kit failed to start, saying it couldn't connect to SQL.

So I check my system and find that SQL 2005 is not installed.

So I download another 54Mb and run the installer. This time it tells me there are bits of beta versions left in the system that I must remove before installing SQL 2005 Express (but not telling me where).

So...

The "uninstall" options have failed to properly remove the beta versions.

The "install" option including SQL as part of the Web Developer Express failed to report a problem during installation.

The "install" option for SQL fails to tell me what exactly is left over. Without any hint of what may be fouling I can only nuke my system and go for a fresh install of everything.

With this encouragement to go back to a low-level format before starting up this learning curve, what's to stop me reviewing my options OS X 86 Linux