This message often relates to a problem with Apple software update.
Go to Add remove programs and find Apple Software update. Try repairing it.
Select Change>>repair.
That probably will not work
Then try uninstalling any instance you find of Apple Software update. That probably will not work either.
Download and install Microsoft Installer cleanup utility, there are instructions on the page as well as the download. Note that what you download is the installer not the program – you have to run it to install the program.
http://support.microsoft.com/kb/290301/
To run the program – All Programs>>Windows Install Cleanup
Remove any instance you find of Apple software update with the cleanup utility.
Download a fresh copy of the iTunes installer and save it on your desktop.
http://www.apple.com/itunes/download/
Restart your computer and try installing iTunes.