Laptop broken, how do I diagnose what is wrong?

So, one fucked laptop here. Machine is a Toshiba Satellite A300, four-five years old, all drivers up to date, no software or hardware changes between Sunday and today. Updated to Win 8 six months ago, has run passably until today, with occasional crashes on hibernation.

Rather odd symptoms: it will boot fine and let me sign in, all the way to the Win8 Start screen, clicking on the Desktop gets me the desktop, but then no further responsiveness. No response to mouse clicks, key presses, CTRL-ALT-DEL. So then:

  • Boot into safe mode, works fine.
  • Try refresh, can’t make a refresh disk in safe mode, can’t do anything in unsafe mode. No refresh possible.
  • Try reinstalling Win 8. No reinstall disk, running the Win8 setup utility from safe mode fails with no error message.
  • Umm… fucked if I know…

So, lazyweb, what should I do to try to diagnose what the problem is? Or should I just take it to the Toshiba service place in town who, truth be told, have been great at fixing hardware problems on several Toshiba laptops. Or should I just stump up an irritatingly large chunk of cash to replace a laptop that’s only four years old?

Before anyone says “don’t use Windows”, I’ll just point out that I’ve been using Linux since Redhat 5.2 and the current set of mechanical or electrical design software for Linux is a heap of shite. And I trust you all know me well enough not to suggest I use a Mac.