I was originally going to tell you to 1) export your contacts into the SD card on your phone in vcf format. 2) then remove the card and insert it into your laptop and 3) edit the vcf file to remove the duplicates and then 4) reinsert the SD card into your phone, 5) delete all your contacts on your phone and then 6) import the contacts on the vcf file back into your phone.
However in searching for a tool to edit the vcf file on your laptop (in order to remove the duplicates) I came upon this webpage talking about software to manage your android contacts (via your PC or Mac).
By installing the software on your laptop, you would then connect your phone to your laptop (via USB) and then use the software to edit the contact file on your phone directly.
Note: in the future you might want to consider the following: I keep all my contacts as google contacts on my gmail account. On my phone, all contacts are google contacts that were sync'ed with my google account. That way if the phone gets lost or destroyed, when I get a new android phone to replace it (or I have to wipe my existing phone completely to start over), once I set up my gmail/google account on the phone, all my google contacts will be downloaded into my phone contact file automatically. Then afterwards if you ever add a new contact using your phone make sure it is a google contact so it will be sync'ed with your contacts stored at google.
That way no matter what happens to your phone, your contacts are safe.