Can't install .net framework 3.5? Solved

Updated

Many people can't install .net framework 3.5. And I was one of them. After many attempts I solved the issue.
I downloaded the updated Aaron Stebner "dotfix cleanup tool" from here  in the page top left and launched it. This tool clean your system from any net. framework trace. After cleanup you can safely install the .net framework 3.5. Maybe the Aaron Stebner dotfix cleanup tool fails at the first attempt.
Then follow these steps:

1. Download "Free Uninstaller 1.1" form this link: http://www.anarchia.com/link_in_frame.php?link=4906&c=
2. Free Uninstaller 1.1 is a zip package.  Doesn't need installation.
3. Double click on it
4. Will appear some registry keys red highlighted on the top of the window
5. The red highlighted registry keys are invalid registry keys. Remove them.
6. Retry with the Aaron Stebner dotfix cleanup.

Now of course you'll be able to install .net framework 3.5.