Windows 7 64bit freezing randomly

Lately my laptop has been freezing randomly. The only solution is to hold the power button to restart, i.e crtl alt del doesnt work.

It 'seemed' to start when i was watching tv on my laptop using pinnacle tv centre pro, but it has been happening on other occasions.
the last time it happened i was running VLC player, Google Chrome and Bittorrent, if this helps but i thinks its just random.

.also i have checked for viruses etc. with trend micro and malwarebytes nothing is found.

I have run the BSOD tutorial and scan.

I ran the seatools tests; short generic, smart and short drive test on both hard drives, they all passed.

I started the CPU stress test but stopped it (and no errors found) when the temps got up to high 90s, should i let the test go longer when the temps are at this level?

Also, from memory, the freezing has only been occuring while watch videos, movies etc on VLC player, and TV on Pinnacle TV centre Pro and Windows media centre.

Ok, I've cleaned the fans, there was a fair bit of dust there, and did the stress test again and temps were around 75, thank you.
i ran the memtest for 2 passes and no errors found,
so hopefully it was the heat thing.
I will update if i am freeze free.
Thank you very much.

2 passes for Memtest is not enough - suggest running 7 passes. Generally, most errors are usually occur around 5 or 6.

OK, im first gonna check if the freezing has stopped from cleaning if not i will run more tests, i stopped it at 2 because i wanted to use my computer.

My best suggest is to do the Memtest overnight.
A sleep for a person takes 8-9 hours and 7 passes for Memtest is around 7/8 hours.