IIS doesn’t do load balancing. You’ll need a load balancer to handle the directing of traffic to all the servers. Windows includes one (I think it is only in the Enterprise Edition) called the Network Load Balancer (NLB). Or you can purchase hardware load balancers from Cisco, F5, etc. You can also look at software load balancers which run within a VM under linux which will do the job nicely if the load isn’t crazy high.
Windows NLB will wotk in a virtualised environment. It is available in all editions of Windows 2003
through to Windows 2008 R2