Ive never messed around with my power options, only to have the monitor turn off after 15 mins of idle. But now with a growing electricity bill I'm thinking about having my harddisk turn off when not in use (especialy overnight!). Is that safe to do and actually worth it? Will it really make much of a difference how much power is used? I hear that the wear and tear on the harddisk may not be worth it, is that true?

Thanks.