Merged Outlook contacts give many duplicates

Hello,

We just bought a CRM software and until today, each salesman had his own contact list in Outlook. I retrieved, for each of them, XLS files from Outlook and I copy-pasted it in one file. Thing is, now I have hundreds and hundreds of duplicate records :( .

I would like to get rid of all the duplicates, how can I handle this easily?

Thanks!