I am using Excel 2010 and the process of finding duplicates is really straightforward:
Select your column –> From Home tab –> Styles group –> Conditional Formating –> Highlight Cells Rules –> Duplicate Values.
But in excel 2003 things are different – there is no built-in formula to find duplicates. So again we have to select our column (let’s suppose it’s column A) go to Format–>Conditional Formating–> Formula is insert the following formula =IF(COUNTIF($A1:$A$1;$A1)-1>0;TRUE;FALSE) go to Format and choose a background color for the duplicate records.