I am a total beginner with databases and had the same problem: Having edited the wp-config-sample.php file with a text editor (NotePad) and renaming it to wp-config as instructed I finally realized that it had been saved with a .txt extension. After editing the file using Dreamweaver which preserved the .php extension everything is fine; I presume the same would happen if I had instead renamed from within NotePad to a .php extension. I hope this helps.
