You can tell if SP2 has been installed by checking your system with BELARC. If you haven't got this installed then download the free program from here and install it on your PC.
SP2 takes around 20 mins to install. It checks
your config. makes a backup, creates a restore point before installing the files then it does a cleanup before you click on finish. I have installed this on two PC's from 2 separate downloads and on two other PC's using the free SP2 disc from PC magazine. Have had no trouble with any of the four PC's.