By default when you move cells to a location already containing data, Excel
will ask if you want to overwrite the contents of the destination cells. In
Excel 2000 I had the option to turn this message off and it would
automatically overwrite without asking (I could always use Undo if I made a
mistake). I can't find anywhere to do this in Excel 2007 and searching for
"automatically overwrite destination cells without asking" has come up with
nothing, either in the Help files or online.

Where have they hidden it or have they removed it altogether?