It is a very common issue with Laptops, phones and tablets. When your computer has a virus or suddenly shows a question mark and doesn’t boot it is usually due to a corrupt operating system. Another reason why you will need to reinstall an operating system is when you upgrade the operating system and it is not compatible with the laptop. You cannot download the previous operating system so you will have to have Macguys to reinstall the operating system. The process is very fast and easy to execute. The only thing to take note of is that all you will lose all of your data stored on the hard drive.