Cannot update iTunes in Windows 7 - download will not complete.

When my software updater alerts me that itunes needs to be updated and I try to download the latest version, I keep running into problems with the download. This happens regardless of internet connection speed, other programs running, etc. The download simply stops halfway through and eventually I get an error message saying the download wasn't completed. I've tried going through both iTunes ("check for updates) and my windows software updater. Suggestions??