If you downloaded the official build (which 136 sounds like it is) you're going to need to be on Froyo, since it'll be expecting the Froyo kernel. If you're not and you install the zip you should have your SBF file ready, since you'll be needing it shortly. If you're on 605, then you want to install the latest "unofficial" build from RevNumbers, which uses the Gingerbread kernel. It's much better anyway.