There is no Service Pack 2 for Windows 7. In May 2016 MS released an update roll-up package. This just bundles together Windows updates released after service pack 1 through April 2016 to simplify updating Windows 7 installations or re-installations. Unfortunately, some mistakenly called this a Service Pack. This caused a good deal of confusion as users started to expect to see SP2 shown in system information and sometimes thought they were missing a non-existent service pack.
If your Windows 7 PC is up to date through the normal Windows update process there is no need for the update roll-up. If you are having a problem with Windows updates, please explain the issue and we can better advise.