Convert SQL 2008 cluster to standalone

1. Assume the SQL server was shutdown gracefully.
2. Remove Windows Cluster Role:
1. Remove the server from cluster (only needed if you cannot remove Cluster feature at Windows Server)
1. Run powershell as an administrator
2. Enter:  Import-Module FailoverClusters
3. then clear-clusternode
2.  Remove Cluster Service.
3. Reboot the server
4. Go to Disk Management, online those cluster disk manually.  Then you can find those disk at Windows Explorer
5. Add the virtual IP(s) to NIC
6. Add the DNS A record to DNS server of old SQL virtual hostname
3. Remove dependency of Cluster service to SQL server
1. Change registry key SqlCluster in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\MSSQL.x\Setup\ from 1 to 0
2. Take a backup and delete HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\MSSQL.x\Cluster
    
4.  Start SQL server via Services
5. Change SQL service start mode from Manual to Automatic.

Tested on Windows 2012 + SQL 2012, and Windows 2008 + SQL 2008