If you are having issues updating iTunes on your Windows machine, you may find the following articles helpful:
I'm having this same issue!!! I've tried everything! All the troubleshooting & all! My itunes worked fine but when I did the update to ios 7 on my phone & hooked my phone to my computer it said I had to update Itunes so I've tried about 100 times & i keep getting the "log in as admistrator" message! I'm logged in as the adminstrator!!! This is so aggravating! Please tell me how to fix this issue so ill be able to snyc my phone!!!!