clear the file system transaction log
Click the Start button Picture of the Start button. In the Search box, type Command Prompt, and then, in the list of results, right-click Command Prompt, and then click Run as Administrator.
In the command prompt window, type fsutil resource setautoreset true C:\. (This assumes that C: is the drive in which Windows Vista is installed. If Windows is installed on another drive, change the drive letter accordingly.)
Restart your computer.
Download and install the update again.