If the order is important, Insert a column in front of column A and create a numbered list (1,2, 3,4, 5, etc down the column)
Sort the spreadsheet on the column that has the duplicate
Then insert another column before column a
enter this formula in a2 (if c is the dup column otherwise use the correct column letter), =c2=c1
copy the formula down in column A
select column A and copy
Paste Special Values only back into column a
Sort on column A
Delete all the rows that says true (they should be grouped together after sorting)
Resort on the numbered column or column B
Delete the numbered column

Questions?