You did what exactly?
When a computer is too old or tries to run too much software at once, it can overheat, which is a common issue that many people encounter. Most people cannot afford to upgrade to a bigger and better computer because they can cost thousands of dollars.
Thus, the best course of action is to update or upgrade their current one. However, given that this “repair guy” really did more harm than good, it appears that the owner would have been better off simply purchasing a new one.