How to convert in OpenERP from one chart of account to another?
I needed to do similar.  It is possible to massage the chart from one form to another but I found in the end that creating a New Database, bringing in modules, assigning the new Chart and then importing all critical elements was the best and safest path.
If you have a lot of transactions that will be more difficult to do the import on.  If that is the case, then massage your chart from one form to another.  
I am sure there will be some way to do an active Migration sometime in the future.  You defintely don't want to live with a bad chart or with out your history if you can help it.
I have installed chart of accounts A for company1. This chart was used couple months for accounting. How can I convert into chart of accounts B and keep old data for accounts (debit, credit, etc.)? In other words, is possible migrate data from one chart of accounts to another? Solution could be programmatically or trough web client interface (not important). Virtual charts of accounts can't be used. Chart of accounts B must became main chart with old data. 
Every advice will help me a lot. Thanks