Still unable to iTunes 12.1.2

I have attempted several times to download iTunes 12.1.2 but installation has failed. I can still use iTunes and update both my iPhone 4 and 5c. I usually receive a very generic response upon downloading that errors occurred, it could not be installed and that I needed to try to do it manually. I just tried downloading again and received the following message: "iTunes has an invalid signature. It will not be installed."

I have tried researching possible solutions. I am logged on as the administrator on our laptop. I have Windows 7 and no updates are needed. Unfortunately, I have not found a resolution to my issue. Any help would be greatly appreciated.