I just hooked up my imac to an external display. It's my 1080p HDTV, it's connected via the mini-dvi to dvi and then dvi to hdmi. When I first connected it all that was on the TV screen was the background so I put on mirroring mode and then everything came up fine. I went to use just the imac and turned off mirroring mode and now spaces is all messed up, it shows 8 4 off set from 4 others it seems like there 2 screens per each space. I put back on mirroring mode and it works fine. How do I go back without using mirroring ode and fixing everything?