A significant change in Windows 7 volume activation is that you must have 25 physical or virtual machines for the KMS (Key Management Service) to become active. This is different than with windows Vista where you needed 25 phsyical machines for the KMS to start activating your machines.
If you already have a KMS you need to install a patch for it, a patch that will be available soon. You also need a Windows 7 license and also to activate it. Read more about the KMS patch at this blog.
Starting with Office 2010 the new version of the KMS will also serve activations for Office for the first time. Office 2010 will be released some time in the first half next year.