Hi aaron.
The problem is in the registry.
please delete the next keys:
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Installer\Products\ClassID###
where "ProductName"="Microsoft SQL Server 2005 Reporting Services CTP instanceName"
[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Installer\Products\7DDFFFA258DE09A4C825D59ABECDB9F8]
"ProductName"="Microsoft SQL Server 2005 Express Edition CTP (SQLEXPRESS)"
[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Installer\Products\A00BD289E4C9B6347870811E31AB4AC4]
"ProductName"="Microsoft SQL Server 2005 Analysis Services CTP (########)
[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Installer\Products\B29A3732C1C117E44B49C59AF769AA91]
"ProductName"="Microsoft SQL Server 2005 CTP (#######)"
[HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Installer\Products\D268E2117227E6845895AEE990231381]
"ProductName"="Microsoft SQL Server 2005 Analysis Services CTP (#####)"
and try again with setup.exe