massive and constant fps drops

hi

so i downloaded tbc from this site eager to play it but i get massiv and constant fps drops
it makes the game completly unplayable

i dont have problems with other xpacs or even retail

any suggestions what i can do?

kind regards

so it seems that if i use plain windowed mode, the fps drops stop
with fullscreen and/or windowed maximized i get the fps drops

now the thing is .. plain windowed mode looks like crap with the taskbar at the bottom and the white window-boarder at the top

as of now i can play some but i realy realy wish someone has a solution to my problem, bc i dont know if i can go on/get the feel like this

little bump