EC2 Reserved Instances - Currently have micro what to do now?

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http://serverfault.com – I have been running with 2 micro on demand instances. I now want to convert one of the servers to a small instance. I have purchased a Windows small reserved instance in us-east-1b and it is now appearing under "reserved instances". My micro instances are also in us-east-1b and are running Windows. Do I need to create another instance? I've looked at doing that but there is nowhere to select to use the reserved instance. Also, the EBS volume still says 30GB when creating that when the AWS website says it should be 160GB. I'm confused as to what I should do. Do I simply upgrade one of my mic (HowTos)