Execute the following steps to reinstall SQL Server in case the current installation is corrupt:

1. Take full backup of all databases.
2. Script out logins, dts-s, configuration, and replications.
3. Script out jobs, multi administration, alerts, and operators.
4. Check for custom extended procedures, export them if any.
5. Make sure your database-id's are the same if you chose for
restoring sys databases.
6. Detach user databases.
7. Reinstall SQL Server (uninstall + install + service pack).
8. Check your registry for orphaned sql server entries (export and
remove them).
9. Rebuild your SQL Server by attaching databases and running scripts
from previous steps.
10. Reindex all databases with sp_MSforeachtable @command1="DBCC DBREINDEX ('?', '', 65)" .

11. Recreate all statistics if db is not in autoupdate statistics mode .