I have snow leopard: my mail changed so I now have to double click to read a message.Want it back so can preview before open.

What version of mail do you currently have? You should have 4.6. If you haven't then you should use the Combo update. That should resolve matters.

Mac OS X 10.6.8 Update Combo v1.1

But you still have to double click to open messages.

With the mail program open, look for a small dot in the center bottom of the display window. Drag that small dot upwards to reveal the preview window.

Go to Mail menu and click on Mail > About Mail . and that will give you the version number.

Just click on the blue link .

Neither do I to be honest. Unusual that because he is so reliable for an answer and chances are he is right, just approaching things from a different direction.

Anyway, 4.6 is right but sometimes things go awry. It will do no harm to apply the update by clicking on it. Then do software update to bring your system right up to date.

Hopefully this helps. And hopefully I haven't misunderstood your question. For the issue of the location of the various headings (From, Subject, Date, etc...) you can simply grab the particular title bar and move them to the location of your choosing.

Open a mailbox. Select a message with a single click. Hover the mouse over the dot in the bottom bar: you should see the cursor change to a up-pointing arrow with a short horizontal line below it (unfortunately I can't screen-grab this). Click-and-hold and drag upwards. Nothing will happen until you've moved it up around half an inch, then the preview pane will appear. Continue dragging until it's the size you want then release.