When a laptop starts to slow down, your only option is to buy a whole new one. Depending on what you need a computer for, a new laptop could cost thousands of dollars.
That's because you have to buy every single part inside the laptop brand new — the processor, motherboard, RAM, hard drive, and everything else. But most of the parts in your old laptop are probably still fine, and it's usually only the processor (and the motherboard it sits on) that needs upgrading.
With a desktop and a little know-how — or some handy YouTube videos to show you — you can easily replace an aging processor (and motherboard) for under $200.
That said, all-in-one desktops are often Apple desktops like the iMac and MacPro can't be upgraded.