Itunes Install Problem

ok so when I try and update my itunes, it gathers all the files but then when it tries and installs itself it says that it cant find the itunes.exe setup file, even though i hit browse and I can see it right there.
Answer #1
when you browse to the file and select it what does it say? mabe you should try uninstalling itunes all together and reinstalling the latest version
Answer #2
it says that either its like not a valid file type or im not connected to some server to access it. i think thats a bit wierd
Answer #3
Download iTunes, install it over a previous version.