This link shows frames per second with various graphics chips in different games, including WoW. http://www.notebookcheck.net/Computer-Games-on-Laptop-Graphic-Cards.13849.0.html
Is your 1545 the single core Celeron variety?
To answer your question, Intel integrated 4500mhd will run WoW on low settings at about 35fps. I'm guessing they measured this in the beginning areas, the higher level areas get more graphically demanding. A dedicated graphics card would work much better. In parties, raids, and populated cities a fast dual core cpu will keep your fps from diving. You could play alone, but that isn't what a MMO is really all about in my opinion. A single core with intel 4500 can run the game, but I wouldn't recommend it.