I was just having this issue as well. I tried the top answers to this and no luck. Just to be clear, I am on Windows 7 and just did a fresh install on a new SSD drive. iTunes was running perfectly on my old version of Windows 7.
When I would download iTunes and "run as administrator" only iTunes itself would actually install. Then when I opened the program, a popup would say that Apple Application Support was not found. Well then why didn't you install it with iTunes, Apple?
Long story short, the fix is this...
Once downloaded and saved, (do not "run") use a program like win-rar to extract the files to another folder. Win-rar was free wherever I found it. You extract by right clicking your download and hitting the proper message. Go into the newly created folder and starting at the top, begin installing the software. Go figure, Apple Application Support is in there! Make sure you install everything including Bonjoir, Update, and the x86 versions even if you have a 64 bit computer. Once everything in there has been installed including iTunes, you should be set. If not, completely remove all iTunes restated software in control panel including Bonjoir, Update, AAS, etc... Once removed, go through the above steps again but in the order they are in that extracted file.
Where I got into trouble and was having the freezing issue as mentioned was not installing the Update program and the x86 versions. Once I did that, everything worked fine.
I hope this helps someone trying to put a movie on their iPad or iPhone for their kids to watch in the car or on a plane.
