WordPress Directory Error::wp_upload_dir()

Ok, I was using Serendipity and I wanted to convert to WordPress. So I made a folder called WordPress and placed WordPress inside of it, then I decided to replace Serendipity by moving WordPress into Seren.’s folder. Before all of that, I changed the WordPress directors under the options to the directory name I was moving it to.

However, repetedly, anytime I try to upload something in WP, it will say UNWRITABLE TO /www/WEBSITE/[Old Folder Name].

Where can I fix this!!