Unable to Install .Net Framework 3.5 SP1 on Windows 7 Ultimate

Unable to Install .Net Framework 3.5 SP1 on Windows 7 Ultimate

"Trying Windows 7, I am Unable to Install .Net Framework 3.5 SP1 on Windows 7 Ultimate..
First I downloaded the bootstrap version then the full version but nothing happens.
I run the install, the UAC prompts and then nothing happens.
No error message or anything."