An update released by microsoft was downloaded and "installed". Every time I turn off my PC with Windows XP Home edition it tells me there is an update to install. The same update. It doesn't want to install.
What update do you mean?
it wont work and Norton isn't installed properly and the install of the update still thinks it needs installing after 1 week + of stupid time.
Try
Norton Removal Tool.
Boot to safe mode and rename
C:\Windows\SoftwareDistribution to something else. This should purge any corrupted windows update downloads.