http://support.apple.com/kb/HT1923
Use the Control Panel to uninstall iTunes and related software components in the following order and then restart your computer:
- iTunes
- Apple Software Update
- Apple Mobile Device Support
- Bonjour
- Apple Application Support (iTunes 9 or later)
You have to uninstall in order
Even if the apple mobile device does not seem to remove ignore it and move on thru list
once everything is uninstalled restart computer
then go download and install again...
This works for most.
I a windows 7 home premium user aware of the issues chose to just make sure itunes was closed, went in to the start button and search field typed in services, waited for it to open clicked services, located the apple mobile device support, clicked stop service then went and downloaded itunes, skipping all the uninstall steps and it worked wonderful!
Good luck!