1) It would help us if you filled out your signature so we can see what type of system and software you are using.
2) There are 1''''s of people using LR that don't experience your problem so it *may* not be a problem with LR but something specific to your system, I think it's little early to start blaming Adobe.
3) Can you test other software that will generate CPU activity, exporting an image in photoshop or another editor.
4) when you say "it shuts down the computer??" does it do a proper shutdown or do you see a blue screen with errors or does it just hang etc ?
5) Check that your operating system and all the drivers are up to date, especially the graphics card driver.