Try taking the battery out. It might run fine on the adapter power and what’s more the dead battery won’t eat any more power. If it blows up, well, you haven’t lost anything, have you? 
I’m typing right now on an old laptop with a 1.2GHz processor and 256MB RAM running as a thin client. Power consumption is 17W. I might be able to lower it a bit more if I open it up and disconnect the flaky DVD drive.