I got a free Dell M4700 from work under the same circumstances. Kept locking up and IT tossed it.Macbook Pro was on the fritz yesterday. It would just shut down whenever I opened Cura (a problem, since I needed to slice some shit for Lily's project).
I figured a fan had failed or something.
Took the bottom off of it (stupid 5 point screws and all), and took it out to the garage and gave it a real good blowjob. I don't know how it managed to collect that much dust, but the fins on the heat pipe were more or less totally clogged.
Anyhow, shit works great now!
Taking the thing apart to get the entire thing clean was a shitty job, but hey, free laptop which is more powerful than anything else in my house.