Every week or so when using Firefox my whole PC suddenly freezes and I have to hit the reset button to get any reaction from it. No other input has any effect.
When this occurs I'm using Firefox, so I assume it is related to it as it is the only common thing. At least the only one I've been able to identify so far.
If it freezes the whole computer then it sounds like a problem with a system driver or security software.
You can use the Autoruns utility to see which software and services gets started.
OK any hints what I'm looking for?
It is likely not easy to investigate this if it only happens once a week like you wrote.
Is there any software scheduled to run (e.g. cleanup of index) at the time when this freeze occurs?