Why does the window roll up slow? Can I correct this problem

It could be a few things, I noticed in my mom's regal if you are trying to roll the drivers window and the passenger window and shut the sun roof, the passenger window rolls up really slow. GM said this is common. They said the more power items you are trying to work at one time, the slower everything will move. Also it could be a bad motor, this is not that hard to acess, but I am not sure how to work on it.
I hope this helped..