Go to the AOPEN website, they usually explain how to recover from a bad flash of the BIOS... if not, then post your mainboard specs (what AOPEN mainboard, what BIOS, etc.)
and do LET US KNOW WHAT YOU DID BEFORE YOU ENCOUNTERED THIS PROBLEM... as it could just well be that you knocked something loose inside of the case when you took out the Battery... check your GFX card if it is seated correctly...
Ben