14. Check to see everything's working
Before I returned the EliteBook to service, I wanted to verify everything inside was working properly. I used HP's Support Assistant software, which came with my EliteBook. A good alternative is AVG's TuneUp Utilities 2014 ($50; free 15-day trial), which can do everything from removing duplicate files and cleaning up a hard drive to fixing Registry problems and making the system start faster.
It's also a good idea to make absolutely sure that your upgraded notebook can take the heat. I use the PassMark BurnInTest ($39; free version available), which runs a variety of tasks simultaneously while noting any faults. This is harsher treatment than you'll give it on a normal basis, but it is a good test of the system's mettle.