It depends on how bad it is... If you window is jammed though... I'd say no.
If the steel cable is kinked... you are fuked. No two ways about it. Even IF you could get the proper tension... Then next time that kink goes over the roller... It would derail all over again and get tangled up.
I'd look up Pelicanparts.com... That's where I always buy mine... Yup... I've replaced 3 of them... You need to make sure you roll your windows down every now and then. If you don't.. They will stick in their tracks just long enough to break the cheap plastic roller on the regulator.