This could be happening if the updates that you are trying to install are corrupted during the process. To stop this from happening
all the time you may have to uninstall the updates and install them one at a time.
For that you will have to make a list of the updates that are causing the problem, then go to install update history and uninstall
them manually. Later download those updates and install them in Clean Boot mode.
To help troubleshoot error messages and other issues, you can start Windows Vista by using a minimal set of drivers and startup
programs. This kind of startup is known as a "clean boot." A clean boot helps eliminate software conflicts.
Steps to put the system in Clean Boot are as follows:
1.Log on to the computer by using an account that has administrator rights
2.Click Start, type msconfig.exe in the Start Search box, and then press ENTER to start the System Configuration Utility.
If you are prompted for an administrator password or for confirmation, type your password, or click Continue
3.On the General tab, click Selective Startup, and then click to clear the Load startup items check box. (The Use Original Boot.ini check box is unavailable.)
4.On the Services tab, click to select the Hide all Microsoft services check box, and then click Disable all
Following this step lets Microsoft services continue to run. These services include Networking, Plug and Play, Event Logging, Error Reporting, and other services. If you disable these services, you may permanently delete all restore points. Do not
do this if you want to use the System Restore utility together with existing restore points
For further information on clean boot please follow the below given link:
How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7
After you have finished troubleshooting, follow these steps to reset the computer to start as usual:
Click start, type msconfig.exe in the Start Search box, and then press ENTER.
If you are prompted for an administrator password or for confirmation, type your
password, or click Continue.
2.On the General tab, click the Normal Startup option, and then click OK.
3.When you are prompted to restart the computer, click Restart
You may also have to reset the Windows Update components, download the Microsoft fix-it from the link and run the wizard which
automatically resets the windows update components, if this does not work, I recommend that you reset the windows update components manually from the link:
These steps should fix the issue, give it a try and check if you are able to perform windows updates.