Found this thread and decided for a final last attempt at curing the boot problem, mouse issues and constant fan noise.
I have two boot problems, th eorange light issue, and also one where it sits on the F10/HP screen for an absolute age - this latter was fixed by removing a CD from teh drive when booting (doh!).
I found that a small black cable (for the touchpad?) had been caught under one of the central securing screw columns. I untrapped it, and now the laptop boots fine and my intermittent mouse issue has gone away! I wonder whether this pinched wire was causing a hardware detection issue on boot..?
I pulled apart the fan and removed a huge 'mat' of dust etc. Laptop now runs cool with the fan running only on boot and really heavy demand.