Hi,
Thank you for asking question in Microsoft Community. I will give my best to help you.
Perform the steps mentioned below and check in it helps:
Method 1: Refer the article below which has the relevant steps pertaining to your issue.
http://support.microsoft.com/kb/923100
Try to fix the issue by running the .Net Cleanup tool that has been provided in the above link.
Once done with that, (re)install all .NET Framework versions manually using the download links on the page.
Method 2:
Step 1: I would suggest you to perform clean boot and check if the issue persists.
How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7
http://support.microsoft.com/kb/929135
Note: Follow step 7 from the clean boot article KB929135 to reset the computer to normal mode.
Step 2: To download .Net framework 3.5 SP1, refer the link below:
Method 3: Try the steps from the following link:
Unable to install updates in Windows Vista, Windows 7, Windows Server 2008 and Windows Server 2008 R2**http://support.microsoft.com/kb/2509997**
Note: This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article:*Back up the registry in Windows Vista*
Note: While performing chkdsk on the hard drive if any bad sectors are found on the hard drive when chkdsk tries to repair that sector if any data available on that might be lost.