i don't know about vista, but i tried windows 7 these days. it's pretty similar to vista, though. first unhide system protected files and file extensions from control panel. then go to your windows partition (e.g. c) and look for the folder users (it's Documents and settings equivalent from XP) go under your user name -> app data -> roaming (the path may not be exactly like this, but pretty close, i'm on xp now). i couldn't find it either when using the search function.
I tried this at my wacom I4 , I think this could be necessary because int4 just eats pen nibs.
I might take 80-85% instead of 75, because this was needed for the 1024 PPlevels, and the 2048 gives a lot of feeling. Also anyone noticed that in the wacom_tablet.dat file, the maximum wasn't 2048 but 2047?