system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do computers get slower?

what are the main reasons? Hard drive, motherboard, fans?
gpt
The computer itself does not get slower. As you use your computer, you will over time adjust settings, install new software and update existing components. New software and settings can add additional load to your system.

Over time, the operating system may also be updated, and add new features. In addition, your data storage devices may become cluttered with old data.

The usual way to "fix" this problem is to reinstall the operating system. However, since you will likely wish to add the software you were using before back, you'll still be faced with reduced performance.

In the end, as software gets better, it takes more processing power. Your computer doesn't get faster unless you update it in some way, so it seems to get slower over time as you do more with it.