If you are unable to install Dropbox software on your Windows environment, please try the following.
If your attempt to download the installer fails, check your system for any antivirus software. McAfee (for example) will often see the installer as Cryptolocker and block you from downloading. Before turning of your antivirus software, it a good idea to do an update as an update may rule out false positives. It also gives you the chance to catch any dormant malware and viruses that are awaiting the antivirus to be turned off.