Windows Vista-Updates won't install

Do you get any errors related to updates?

1. Open Windows Update by clicking the Start button , clicking All Programs, and then clicking Windows Update.
2. In the left pane, click View update history.
3. Find an update for Windows that has failed to install, and then double-click the update to view more information.
Updates that have failed to install will display Failed under Status, next to the update name.
4. In the Windows Update dialog box, next to Error details, review the error code for the failed update.
5. Either follow the links in the Windows Update dialog box under More Information or Help and Support to try to fix the problem, and then try installing updates again by using Windows Update in Control Panel or post back with the error code so perhaps someone may be able to assist further.

What are error codes and how can I use them?
http://windows.microsoft.com/en-US/windows-vista/What-are-error-codes-and-how-can-I-use-them

General Windows Update Troubleshooting

Suggestions:

How do I reset the Windows Update settings?
http://support.microsoft.com/kb/971058

Register Windows Update engine files
http://support.microsoft.com/kb/326253

Rename the software distribution folder

1. Stop the Windows Update service (make sure you are logged on as an Administrator)

Start button || Control Panel ||System and Maintenance ||Administrative Tools
Double-click Services
(Provide the Administrator password or confirmation if prompted to do so.)
Right-click the Windows Update service and click Stop.

2. Click Start, type %windir% in the Start Search box, and then press ENTER.

Locate and rename the SoftwareDistribution folder.

3. Start the Windows Update service

Start button || Control Panel ||System and Maintenance ||Administrative Tools
Double-click Services
(Provide the Administrator password or confirmation if prompted to do so.)
Right-click the Windows Update service and click Start.

Important:  Restart the computer, and then run Windows Update again.

Renaming the software distribution folder will erase your history on the Windows Update Site. Anytime you wish to check what updates are installed you can: -
Start button || Control Panel || Programs
Under Programs and Features - click View installed updates.

Rename the Catroot2 folder

1. Click Start, type cmd in the Start Search box, right-click cmd.exe, and then click Run as administrator.
2. At the command prompt, type the following commands, and then press ENTER after each line:  

net stop cryptsvc 
ren %systemroot%\System32\Catroot2 oldcatroot2 
net start cryptsvc 
exit

3. Delete all tmp*.cat files from the following folder:  

%systemroot%\system32\CatRoot\{F750E6C3-38EE-11D1-85E5-00C04FC295EE}  

If no files that start with “tmp” exist in this folder, do not remove any other files. The .cat files in this folder are necessary for installing hotfixes and service packs.

Important: Do not rename the Catroot folder. The Catroot2 folder is automatically recreated by Windows, but the Catroot folder is not recreated if the Catroot folder is renamed.

Reregister DLL files that are associated with Cryptographic Services
Reference: http://support.microsoft.com/kb/822798

Click Start, type cmd in the Start Search box, right-click cmd.exe, and then click Run as administrator.

At the command prompt, type the following commands, and press ENTER after each command:

regsvr32 /u softpub.dll
regsvr32 /u wintrust.dll
regsvr32 /u initpki.dll
regsvr32 /u dssenh.dll
regsvr32 /u rsaenh.dll
regsvr32 /u gpkcsp.dll
regsvr32 /u sccbase.dll
regsvr32 /u slbcsp.dll
regsvr32 /u mssip32.dll
regsvr32 /u cryptdlg.dll
regsvr32 softpub.dll
regsvr32 wintrust.dll
regsvr32 initpki.dll
regsvr32 dssenh.dll
regsvr32 rsaenh.dll
regsvr32 gpkcsp.dll
regsvr32 sccbase.dll
regsvr32 slbcsp.dll
regsvr32 mssip32.dll
regsvr32 cryptdlg.dll
exit

Note: Click OK if you are prompted.

Restart the computer.

Re-Install “Windows Update Agent”.

Download and install the latest version of “Windows Update Agent ” on your computer.

How to obtain the latest version of the Windows Update Agent to help manage updates on a computer
http://support.microsoft.com/kb/949104

Information for network administrators about how to obtain the latest Windows Update Agent
http://support.microsoft.com/kb/946928

To reinstall Windows Update Agent - download the relevant file for your system and save it to a drive where Vista is not loaded because the file cannot be launched directly from the system root directory.

Click Start, click Run, type: "D:\WindowsUpdateAgent30-x86.exe /wuforce" (without quotations) and then press Enter to install the Windows Update engine.

Note: There is a space between "D:\WindowsUpdateAgent30-x86.exe" and "/wuforce"

D: is the drive where Windows is not installed (ie a flash drive or a 2nd hard drive etc)

How to troubleshoot a problem by performing a clean boot in Windows Vista:
http://support.microsoft.com/kb/929135