Itunes 11.1 wont download

Please help, I've just plugged my Iphone in to my pc in order to try and update to ios 7, however when I check for updates it comes up with the messgae A new iphone software (ios7) is available, but requires itunes 11.1, would you like to download itunes 11.1 now? when i click download itunes nothing happens. The text box disappears and itunes freezes for about a minute. Then it unfreezes and i can use itunes again but no downloads have started and nothing has changed.

Please help, Thank you!