Help! I hid the two top rows of an Excel file, and now
I can’t figure out how to get them back because I can’t find a way to
access them to reverse the Hide command.

I sympathize. There is nothing intuitive about this solution, which works in Excel 2003 and 2007. Let’s start from the beginning. To hide, say, rows 3 and 4, highlight the target rows, click on Format, Row, Hide (see screenshot below).
Or right-click and click on Hide.
(See next entry for keyboard shortcuts for hiding and unhiding rows or columns.)
Now, although the hidden rows are not directly accessible, you can
indirectly access them by highlighting the two rows that straddle
them—2 and 5 (see screenshot below).
So if highlighting rows 2 and 5, right-click and just select Unhide and the two hidden rows will appear.
But if you hide rows 1 and 2, there’s nothing to straddle. One option is to highlight the entire sheet by right-clicking on the box above 1 and to the left of A. And while it works, the Unhide command will unhide the entire sheet. That would be OK unless you have other parts of the worksheet you’ve hidden and you don’t want them revealed.
Here’s where you’ve got to engage the not-so-intuitive trick to unhide just rows 1 and 2: Click on F5 to engage the Go To menu. Under the Reference tag, enter the range of the rows you want to unhide—in this case 1:2—and click on OK (see screenshot below).
Although nothing appears to happen, you actually selected those two hidden rows. Now go to the Format menu, click on Row and Unhide, and rows 1 and 2 will appear.