~Insert a column: call it Column A
~Go to the last item in the list, and enter 1 in the new column next to
the last entry: suppose that's cell A50
~In the cell immediately above the 1, or A49, enter the formula =A50+1.
Copy that formula up to the first entry.
~Sort Column A (ascending) over your range of rows
~Delete column A

Vwala!