Aggregates Data.

Hi friends;

I have this 2 aggregates built in Production system and already data sitting there (users are using currently). Now I have designed aggregates in Dev and transported over to the QA and Prod. , Now I have 4 aggregates the new ones are not filled with data. I want to delete the two old and make a use of the new ones, but I don't know how to handle the data sitting there. I have data in the cube..so can I just delete the old aggregates fill the new ones which would take me long time and I think it's not prefrable. Is there other way to handle this situations! Please give me the steps. thank you.

Nitik