Removing approximate duplicates in single column in '03

Hi all,

I am looking to removing duplicates of names of companies in a sheet that has contact information from a number of sources. The first thing I need to do is figure out how to remove duplicates based only on column A. I am using excel 2003 for mac. Will I be able to do this if I simply highlight column A, then data>filter>advanced filter and check unique records only? It prompts me with a warning screen "excel cannot determine what row in your list or selection contains column labels, which are required..."

If so, this will remove about 90% of my duplicates. However, there may be spelling discrepancies in some of the entries. That's not to say that anything will be misspelled, but it might be the difference between "Acme" and "Acme inc". Does anyone know a good way to get around this problem?

Thank you