Removing an entire line if there is a duplicate

you could use a formula like this to tag the duplicates =COUNTIF($A$2:A2,A2) and drag down. This will give a 1 to originals and a 2 to duplicates. Then sort on the column ascending (or descending) with the formula (copy and paste special values first) then you'll have all the duplicates together (2s and above). Then just highlight the entire rows they are in and hit delete.

Two ways to do it.
Use VBA - sorry, I can't help with this.
Use a Sort/Filter/Re-sort.

1. Add another column - label it 'Sort'.
2. In the first data row of that new column, enter the number 1.
3. Continue down the columns: 1,2,3,4...
Once you've done the first 1,2 you should be able to auto-fill down the rest of the rows.
4. Select your header row.
5. On the Data tab, click the Filter button, which will put sort/filter arrows in each cell of your header row.
6. Click the arrow for your e-mail address column and select Sort A to Z.
7. Your data will now be sorted with the duplicate e-mail addresses grouped together.
8. Delete the duplicate rows.
9. Now go to the new Sortcolumn you inserted, click the arrow and select Sort Smallest to Largest. This will put your data back in its original order.

If you have so many rows that seeing and/or deleting the duplicates manually (step 8) will be difficult / very time-consuming, try this:
8a. Select the e-mail address column (I'm going to assume it's column A - change the references below as needed) - so A2:A1000 or whatever.
8b. Go to Conditional Formatting → New Rule → Use a formula to determine which cells to format.
8c. Enter this formula:
=A2=A1
8d. Choose a fill colour which you don't use for anything else. Click OK.
8e. Click the sort/filter arrow on your e-mail address column and select Filter by color. Choose the colour you selected in 8d above.
8f. You now have only the duplicate rows shown.
8g. Select the data you can see (but not the header row).
8g. Press Alt-; (Alt and semi-colon together). This will select only the visible cells in the selection.
8h. Delete those rows.
8i. Click the arrow on your e-mail column header and select Clear filter from label.

That should do it.
If you're not sure about the instructions above, try on a back-up copy first (always a good idea anyway).

Hope that helps - sorry it's a bit long!

I think you are mistaken. Remove Duplicates will remove entire rows. By default, when you select Remove Duplicates the whole data range will be selected and you will be give the option to choose which column(s) to test for duplicates.

That said, I don't think Remove Duplicates was available in Excel 2003, as per your profile.

Which answer are you referring to?