Upgradeproblem SQL-Server 2000 - SQL-Server 2008

Hi,

im trying to Upgrade from SQL-Server 2000 to SQL-Server 2008.

The OS is Windows Server 2003 SBS.

When i run the Setup, the AclPermissionsFacet failed with this message: "Rule 'Consistency validation for SQL Server registry keys' failed'. The SQL Server registry keys from a prior installation cannot be modified. To continue, see SQL Server Setup documentation about how to fix registry keys."

Is there any solution for this?

THX