I turned mine off one night with no problems a few months back and it wouldn't start the next day, pulled the power supply out and went to a store called
http://www.microcenter.com/ and found a new power supply for $24.99 on sale and threw it in and all good, I plan on building my next computer with parts from there on the side when I get time and when I get it done I'll hand my current setup to a family member.