To manually force an update check for windows Vista or Windows 7, go to Start > All Programs > Windows Update.
On the top left, you will see a "Check for Updates" link. Click this:
If any updates are available that have not come through Automatic Updates, they will then be displayed here.
NOTE: After installing any Windows updates, you will NEED to run Windows Updates again. Repeat this process until it confirms that "Windows is Up to Date".
Edited by JimW