Hello Omar,
- Have you logged in as an Administrator on your computer?
- Which program are you trying to install?
- Is your computer on a Domain network or Home group?
Method 1: Try to run an application one time with a full administrator access token.
- Locate the program icon or a shortcut in Windows Explorer.
- Right-click the program icon or shortcut, and then click Run as administrator.
- When the UAC message is displayed, do one of the following:
If you are logged on as a standard user, or if UAC is configured to always require credentials, enter the appropriate administrative credentials, and then click OK.
If you are logged on as an administrator and UAC is not configured to always require credentials, click Yes to start the application.
Note: If you are using CD/DVD to install the program make sure that you have logged in as an administrator and then attempt to install the program.
Method 2: If you still facing the issue you may try running the following Fixit article.
This Fixit will automatically repair issues that block program installation or removal because of corrupted registry keys.
Fix problems that programs cannot be installed or uninstalled
http://support.microsoft.com/mats/program_install_and_uninstall/en?wa=wsignin1.0
Hope this helps, please reply with the required information for any further assistance.