First, please update your Windows 7 with SP1 and subsequent updates.
Once your OS is up to date, please try these steps:
Follow ALL these steps exactly:
Before trying to install .NET Framework 4.0, execute this command from an ELEVATED Command Prompt provided by the .NET Framework Team:
"This issue is likely caused by a bad ACL on assembly\tmp folder. After installing updates, the ACL propagates to installed assembly folders in both 4.0 & legacy GAC. If those updates were installed by WU or another user, the propagated ACL will
prevent install of the same assembly by the current user.
A work around would be to reset the ACL on GAC dirs.
for /F %D in ('dir %WINDIR%\assembly %WINDIR%\Microsoft.NET\assembly /s /b /a:d') do takeown /F %D && icacls %D /reset /T"
After running that command, follow these steps:
Please follow these instructions exactly:
1. Download a fresh copy of the standalone installer for .NET Framework 4.0:
http://www.microsoft.com/en-us/download/details.aspx?id=17718
2. Also, clear your %temp% directory and disable your AV software.
The %temp% directory is a reference to the Temp folder associated with the current user. To clear it, do the following:
Sign on to your system with the Administrator user account you will use to run the installer. Click the Start Orb and type %temp% in the search box. The search results will show the Temp folder you want. Click on the Temp folder to open it in Windows Explorer,
then delete the entire contents.
3. Run the standalone installer from step 1 As Administrator.
Note: Just using an administrator account is NOT enough. To activate full privileges, you must right-click the installer, then select Run as administrator.
If the install fails, provide complete install logs as follows:
Please collect your install logs with this:
http://aka.ms/vscollect
After you run Collect.exe, you'll find vslogs.cab in your %temp% directory. Please upload vslogs.cab to a public site, like SkyDrive, and post the link here.
