Have you tried downloading and installing on a separate computer? ... perhaps even a different computer on a different operating system? ... maybe even on a different network system?

Try the above 3 suggestions if you haven't already. Then worry about finding out why your particular machine is failing the install.

---- Are you logged onto your computer as the Administrator of that specific machine, rather than as a user or administrator of the network that includes the machine?

Do you have 100% access to and knowledge of the internal security system of the computer you are using?

Is there an antivirus/antispyware program running on your system?

John