When I was using Excel 2003, I could easily adjust which direction the cursor would move—either to the right or down—after I entered data in a cell. But Office 2007 doesn’t seem to give me a choice. Is there a way to adjust that default?
There is, and it’s tucked under the Ribbon. And I don’t know whether you realize it, but as you’ll shortly see, you have more choices than moving it to the right or down. To access the default adjustment, click on the Microsoft Office Button and then on Excel Options at the bottom of the screen and on Advanced, which produces this screen:

Notice you have the option of moving it down, up, right and left.
In Office 2003, access the adjustment by clicking on Tools, Options, Edit, generating this screen:

One more option: For some reason Microsoft doesn’t tell you that, in both Office 2003 and 2007, a click on Tab will move the cursor to the right no matter how you set the default.