Ravi, in the release notes it states that you may have to manually removed the registry entry. Check the release notes/known issues for details. ...
[EDIT] From the release notes: To work around this issue, manually remove the registry key at HKLM\SOFTWARE\Microsoft\Microsoft SQL Server\80, and then re-run SQL Server 2008 June CTP Setup.
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Personal Motto: Why push the envelope when you can just open it?
If you follow the direction given HERE[/url] you'll likely increase the number and quality of responses you get to your question.
Jason L. Selburg