That's a pretty broad question. However, generally speaking, you're going to develop your automation in whatever environment you have configured for that. When it comes time to execute against different environments, you have two options that I see.
1) You can create your own virtual machines, one for each version of Windows you want to run the tests on. Install and license a copy of TestExecute on those machines and use TestExecute to execute your tests on those environments.
2) Obtain a subscription/license to CrossBrowserTesting which integrates into the Environment Manager of TestComplete. Configure multiple environments and execute your tests within those environments.
These are high-level answers for a very broad question. If you have more specific concerns, questions, problems, please feel free to post them and the community will be happy to help.