Many suggestions already given. I'll give you different direction.
I am a computer technician. For your case I suggest you to download some free 3D games and play them for several hours. If it does not crash then it passes.
For further test, you can search the Internet and download a free tool called computer stress test. If it passes all the tests then your computer is okay.
Why does a computer crash? There are many possibilities. The hardware, the VGA/GPU, the Windows, the drivers, infected by virus/malware, the bug in the program itself.
Lazarus is not bug free. But Lazarus 1.6 wasn't that bad. It doesn't crash once every several days. My Lazarus IDE never crash, not even once, unless I use it to run ugly code so the debugger crashes.