You don't have 4 processors, you have 4 cores and you can put all them running by setting the process afinity in the task manager.
ET uses as many cores as you have, but it gets fucked up once ET launch etpro, so it goes down to 1 core again. If you want to put 4, you'll have to minimize the game once it's running etpro, and then set the afinity.
Wich is in the proccess list, rightclick on the proccess, and its under "set priority", you can allocate an image to X number of cores in your CPU, i have no idea wether windows will remember this, and re-use it next time the image is run.
It might seem stupid to you but not to me.
ET uses as many cores as you have, but it gets fucked up once ET launch etpro, so it goes down to 1 core again. If you want to put 4, you'll have to minimize the game once it's running etpro, and then set the afinity.
It does not for ET and you have to reselect it every time
but afaik it wont work properly since ET doesnt support it