Conversion: Information no Transfering

Conversion: Information no Transfering

I am putting all my enquiries into the Leads tab. But when they sign a contract and begin our sales process, I convert them into a Potential. However, the information (phone, email etc) does not transfer across for all the tabs, so I loose information. Also, I dont want the conversion to add to the Contacts, because this is where I keep my supplier information.

Can someone tell me how to transfer all the information across to Potentials? Can I go back and edit the tabs to include them in Potentials and Accounts?