Windows has a number of logs that are useful for troubleshooting or making sure that all is in order. …
We'll look at two kinds of logs: the Windows Update log and the event logs. In both cases your goal should be to address all significant issues. Months later when the client calls you back to fix a new problem, you will be thankful that the logs aren't clogged with preexisting unrelated issues.
The Windows Update log, unsurprisingly, records the system's patching activity. Review it and address failed updates as needed. Ideally you will review the entire log, but it is often sufficient to search for the word "error" beginning from the date you began your work.
Next, open the event logs at Control Panel – Administrative Tools – Event Viewer. Do this as an administrative user. Go through all the sections and address issues as appropriate. Logged events are often cryptic; use Event Viewer's event log online help link or the often more helpful Event ID database.
When you have addressed all the issues in the logs, clear them and reboot the machine. Then revisit the logs later to insure that everything really has been dealt with.