Can't install SQLExpress 2008

I uninstalled SQLExpress 2005 (installed through VS 2008), and used
Windows Install cleanup gto make sure everything was gone - although I
notice the SQLServer 2005 config manager is still installed?

Anyway - I get

Error result : -2068643839
Result facility code: 1203

while it is running the setup support files. All the pre-config
checking etc. tests pass.

What do I do to get this installed?

Thanks!