how to move from sub directory to root

I have the latest wordpress installed. Now I am changing my hosting company. When I installed it I have made subdirectory and installed. I had something else in my mind and it did not work out. Now I wish to move the blog to a new hosting. I have already done it. But when I moved all files to root it does not work properly and I had to move to a subdirectory.

Now please tell me how do I move my blog which is installed in the sub directory to the root directory

thanks