This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
It depends. If you're running as a windows service, the logs might be locked by the OS. I'm not sure if they will be re-created or not.
A better approach would be to configure log4j. With log4j, you can set up a rolling appender that will cause a new log to be generated each day. Then, you can easily archive the old ones without interrupting service.