Duplicate display laptop closed sony vaio windows 7

I have my Sony Vaio laptop (windows 7) hooked up via hdmi cable to a tv, works fine but i want to close the laptop lid so it isn't open all the time to dust ect. can i close the lid without it going in to sleep mode or shutting down? How can i do this?


unrelated
Also i have external hard drives hitachi 1 and 2 tb. When should i backup/replace them so i don't lose my data? Are there signs or signals to let me know and are there more reliable options for storing that much data?