When you download the latest nVidia driver and run the installer 2 things happen:
1. The downloaded installer extracts and downloads all the files necessary to do the actual installation and puts these where you tell it
2. Then it performs the installation using the files extracted in step 1.
What you probably did is have the installer extract to the same folder used for the final installation. This pretty much doubles the amount of space used because you get both the extracted files and the installed ones.
What I do to avoid this is to use a temporary folder for step 1, let step 2 complete (it will automatically find the extracted files it needs), and then delete the files in step 1.
Also, the Progam Files directory was established back in the days of 32-bit Windows. When 64-bit became available Microsoft thought it would be a good idea to separate the 32-bit programs from the 64-bit ones, so they established Program Files(x86) for 32-bit programs and planned on using Program Files for 64 bit programs.
Since a lot of program installer software had the name "Program Files" hard coded into it Microsoft created a Junction Link from Program Files to Program Files(X86). This made the installer programs install into Program Files (X86) even though they thought they were installing into Program Files. 64-bit programs were supposed to go into Program Files, but in fact the whole issue is more confusing than it's worth. You can install either 32 or 64 bit programs into either place and they will run OK.
