This issue can be caused by any of the below possibilities. Not enough hard drive space. Left over programs and bad files. Data Corruption. Missing Windows updates or outdated drivers. Computer is overheating. Corrupt OS. Bad Hardware. Tip: This page only cover an overall slow computer and not a computer that has a slow boot up. Below are steps for Microsoft Windows users that should help speed up the computer or determine why the computer is running slow. Reboot If your computer has not been reboot recently make sure to reboot it before following any of the below steps. Not enough hard drive space