Hi Sewer Pipe Salt
sorry hear your still having trouble installing GWX did you install SH3 and the 4Gig Patch outside Program files x86 just on drive C:/ or on another drive like D:/ like in the pic below
if so then install the 4Gig Path then click on the GWX Wolf Paw Icon and then GWX will ask where you want to install it you have to direct it to the wright drive and SH3 Folder like in Pic below it shows drive C:/ thats an old install i reinstalled everything on drive D: just to test it and it worked.
GWX3 Should now start the install process like in the pic below
let me know how you get on we need to get you out in the Atlantic sinking those troublesome tommies