Computer keeps freezing - how do I find problem

[SHARKY7SHARKY]

Well when was the last time you defragged? 3 months 3 years, if Windows is not defragged then it can become unstable & random freezing.
I always work on the bases of eliminating the easy things first then work through major issues.
It could be software problem
It could be memory
It could be the power supply
It could be the CPU
It could be the graphics card.
I have four sticks of memory & if I suspected faulty memory I would just take a stick out to eliminate fault.
You can try a new install it’s up to you.
I myself would keep an eye on the graphics card fan & CPU fan to see if they stop & start.
But I wouldn’t go into the hardware side until I defragged.
I would defrag in safe mode with defraggler after turning off system restore.

[SHARKY7SHARKY]

This is usually the symptoms of a failing hard drive

Strange Noises
Disappearing Data and Disk Errors
Your computer stops recognizing your drive
Computer Crashes
Really Slow Access Times

[lambdj]

An update...

Last weekend I went through the painful process of re-installing windows, which took ages because of all the updates needed after installation. Since then its not froze. I've not re-installed all the software I had on the PC as I'm not sure everything is needed, but so far so good.

Thanks to everyone who gave advice and helped.

[Asyn]

Thanks to everyone who gave advice and helped.

You're welcome..!
Glad your system is up and running again.