Depends on the laptop, as I have upgraded a couple over the years. Usually RAM and HDD/SDDs but there was a Lenovo that I did a CPU upgrade on. It all depends on the laptop. My current Dell laptop actually has a downloadable manual that outlines how to do many different upgrades/replacements. Sounds good, right? Well, a HDD to SDD replacement required disassembly of nearly the whole computer (same for RAM or WIFI card). It was a real learning experience but I'm not sure I'd tackle it again. (Kudos to Dell for creating a very detailed, step-by-step manual which proved indefensible). Some of the newer, super-thin laptops, I doubt an end user can do much with these. Working on a desktop is a piece of cake compared to a laptop!