If you experience an installation error on every package that you download from the Windows Update site:
01. Use Start / Search to search for Files and Folders. Type iuengine.dll, iuctl.dll into the file search box.
02. Delete all occurrences of these two files, deleting the ones in %SystemRoot%\System32 last.
03. Close all Internet Explorer Windows.
04. Use Control Panel / Internet Options to delete your Temporary Internet Files, checking Delete all offline content, and pressing OK
05. Press the Clear History button and YES to confirm the deletion.
06. On the Security tab, select Trusted Sites. Set the security to Low and Apply the change.
07. Press the Sites button.
08. Uncheck Require server verification. Type http://*.windowsupdate.microsoft.com. Press Add and OK.
09. Press OK to close the Internet Options dialog.
10. Use My Computer / Tools / Folder Option / View to check show hidden files and folders.
11. Use Windows Explorer to navigate to %ProgramFiles%\WindowsUpdate, generally at C:\Program Files\WindowsUpdate.
12. Delete every file and sub-folder, except the V4 sub-folder.
13. Expand the V4 sub-folder and delete every file and sub-folder except iuhist.xml, which contains your Windows Update installation history.
14. Disable any anti-virus, browser accelerators, and download utilities that might interfere with the native operation of Windows Update.
15. Try using http://windowsupdate.microsoft.com.
NOTE: Make sure that any proxy server or firewall is NOT preventing Windows Update from working.