This worked for me on Vista:
http://www.gamefront.com/files/21699449 copy the whole battle.net file over the existing file in your C:/Programdata/Battle.net
after that, http://patchup.info/d3/tools/Win/ and aply both patches.
Then finally run the D3 setup as admin.
Game is installed and running atm.
Did everything with 0 luck still.. heading to walmart and buy the collectors pack in hopes it works.
nah I bought the collectors pack, using disc for installation,it was still the same, i can't even get pass the very first Updating Setup Flies. No Install if the updating setup files issue was still there
I have had the same problem. I ended the agent when it stuck at 95% and opened three copies of it as it was restarting. The processes merged, and I did the same thing again. About five mins later the install screen popped up. Ill let you know if it doesn't install, but for now it seems to be working.