It seems that in some cases the scripts on Apple's site that are intended to query your system to offer the appropriate installer don't work as intended, taking you straight to the "Thank you for downloading" page. Depending on the edition of Windows you are running, there are three variants of the most recent version of iTunes, with direct links to the installers as follows:
The third of these - which is actually the 32-bit application with a 64-bit installer - should be used if you get a warning about video card incompatibility when you install the standard 64-bit version, but also may resolve issues with playback, QuickTime compatibility, and problems with some third-party applications (including Outlook).
See turingtest2's notes onTroubleshooting issues with iTunes for Windows updatesfor more details if you're still having problems with installation.