Photoshop help

The other day I decided to turn on "Grid" to straighten an horizon but now I find that the gridlines come on everytime I open a new file and I have to uncheck it manuallly which is starting to get annoying.
Does anyone know how I can go back to the default?
Also, I can't seem to find the "Channel Mixer" command anywhere, I'm using Vers. 7
Thanks for your help.
Does anyone know how I can go back to the default?
Also, I can't seem to find the "Channel Mixer" command anywhere, I'm using Vers. 7
Thanks for your help.