An important thing people forget about PC's is data backups. Backing important stuff up to a cloud and maybe even an external physical disk every so often is vital for making sure you have your important data on hand. Hard drives (including SSD's) eventually fail, and some as early as 5 years.
There's also the chance of having to wipe your Windows / Linux / etc. installation and reinstall it if things go horribly wrong, and having important data backed up is essential then. Windows gives you some free OneDrive space if you register an account with them and link a Windows key. A Gmail / Google account gives you Google Drive, and there's always DropBox, although that gives you the least amount of storage for free.
Also note that the power supply will eventually fail as well, and that's another component that might fry your system and make you glad you backed up your data. Last but not least, don't forget that your OS has to be kept up to date, particularly with security patches, and that when it goes out of support (like Windows 7 and earlier already are and Windows 10 will be next year) you have to upgrade to a new OS that DOES have security updates.
If you can't upgrade to Windows 11, there's always flavors of Ubuntu around, like Kubuntu or LInux Mint with Cinnamon that aren't hard to learn for people coming from Windows.
People in these comments are talking about old hardware that still works 10 years later, and while that's impressive, if the OS on that hardware doesn't have the latest security updates, they shouldn't be connected to the internet, otherwise they're easy targets for hacking and your data on there will be easy to compromise.