Please help us to help you by providing more information. If we were sitting at your computer with you, we would understand what you're telling us.
Since we're not, you'll have to be our eyes and ears.
Which operating system?
Where are you downloading from? Got a link?
Do you have a redemption code or serial number? If so, you can download the current version 5.6 from Adobe:
Win: Adobe - Lightroom : For Windows : Adobe Photoshop Lightroom 5.6
Mac: Adobe - Lightroom : For Macintosh : Adobe Photoshop Lightroom 5.6