A well formed Windows cluster is a pre requisite for a clustered sql server instance.
First you must cluster the Windows operating system on the computer nodes. Once this is done you then have to install the sql server instance as a cluster aware application.
If you're going to be using Veritas Cluster Server or HP Polyserve instead of Windows Server Failover Cluster, then the process is somewhat more complicated.
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"Ya can't make an omelette without breaking just a few eggs" 😉