How do I know that SP2 has

already been installed in my computer?

When I turned on my computer today, a windows update popped up and said it's time to update my computer. Then I just followed the instruction, the installation started automatically. A few minutes later, it said the windows update has successfully completed. Finally I rebooted the PC when asked to do so. But it didn't show me whether it was SP2 or not in the entire installation process.

Are there any other ways that I could check on this? In other words, for those computers that have already installed SP2, is there any record written in control panel or somewhere else?