Windows Vista - How do you tell if it's auto-updating?

My PC recently was slow to start, then it crashed and rebooted. I got a message from the help screen to download Vista service pack 2. As far as I know Vista is on auto-update & I have already got SP2. Not sure tho how to check if this is the case, any suggestions as to how I do this ?

You need to check the status of updates by going to:

Start, control panel, system and security, and then check for updates.

Right click on your "computer" icon on your desktop and select properties or go to Start and right click on computer and properties, this will bring up your system information and in the top under the heading titled Windows edition you will be able to check which version of Vista service pack is installed.
For updates you need to go start and in the bottom left "start search" box that appears type security center and enter or go to Start, control panel, security, Security center.
From here you can check the status of your automatic updates by clicking the down arrow and selecting change settings if necessary.

Thanks everyone, for some reason I missed these posts earlier.