Didn't know you could just buy that part only...both of mine destroyed themselves within a year of each other in the same manner, and I was told that I had to replace the entire regulator w/motor as the part was not sold seperately!
Oh well, each was $140 (just replaced one last week)...
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car