Hi,
- Are you aware of making any changes to the computer prior to the issue?
- Are you able to open the list of programs window in add/remove feature?
Method 1:
To uninstall or install program, you may use this fixit:
Fix problems with programs that can't be installed or uninstalled
http://support.microsoft.com/mats/program_install_and_uninstall/
Method 2:
Step 1: Safe mode
Boot your computer in safe mode and check for the issue.
To start your computer in Safe mode
http://windows.microsoft.com/en-US/windows-vista/Start-your-computer-in-safe-mode
Step 2: Clean boot
If you do not face the issue in safe mode, then put your
computer in clean boot and check for the issue.
How to perform a clean boot to troubleshoot a problem in Windows Vista, Windows 7, or Windows 8
http://support.microsoft.com/kb/929135
Note: Once you are done with clean boot, please follow the section ‘How to reset the computer to start as usual after troubleshooting with clean boot’ under ‘more information’ in the article
to put your computer back to normal startup.
Method 3:
Perform an SFC scan on your computer. Refer to the following link:
How to use the System File Checker tool to troubleshoot missing or corrupted system files on Windows Vista or on Windows 7
http://support.microsoft.com/kb/929833
Provide us with the screenshot of the issue to get more information on the issue.
How do I: Post a screen shot on this forum?
http://answers.microsoft.com/en-us/windows/forum/windows_7-security/how-do-i-post-a-screen-shot-on-this-forum/c86de820-c620-401c-a804-9f6337cd3053
Hope this information helps.