Win7 x64 random freeze, no BSOD, no minidump, no event viewer error

I have a Dell Vostro 3500 - picked it up 2nd hand with a clean install of Windows 7 64-bit.
I noticed it would crash randomly where everything just locks up (mouse keyboard etc, all non-responsive) - so I thought maybe windows updates would fix it, but it appears not. When it freezes it doesn't reboot, no BSOD, no matter how long I leave it, i'm forced to hold down the power button to reboot.

After reading many threads, so far i've:

Ran Malwarebytes
Booted with all non-windows services/programs unchecked
Ran a disk check - no errors
No entries in event log at time of freeze
Left Task manager open until freeze occurred - no observations.
Checked for driver updates (not sure how thoroughly I did this though)
Ran dell diagnostic tests using F12 - no errors
sfc /scannow - all OK.

There's absolutely no rhyme or reason what makes it crash it seems - it has happened after I've started windows and not even moved the mouse yet, and also after hours of just routine use.

I was thinking (hoping not) that it might be hardware, a bad MB or HD, but it seems ok in safe mode. Does this point towards drivers?

If anyone has any suggestions for things to try/test that would be very helpful.

Enable mini dump by ..right clicking 'computer'..properties..Advance System Settings..start up and recovery settings..in system failure..check write and event to system log..write debugging information..select small memory dump..

and this mini dump will be in c:\windows

and its name would be memory.dmp i think

Thanks for the reply.

I have those options selected. small dump directory I set to %systemroot%\minidump.

In this folder, windows/minidump, there are only two dmp files, the latest is around 1 week ago - yet the system has frozen many times since then. Not sure why a dumpfile was created at that point, and not since. Could it be that the system freezing means it can't physically write a dump file..?

Not sure if it's any help, but I ran the DM log collector..hopefully the zipped file is attached.

Have now also performed all tests using SeaTools (except for the advanced testing) - no errors found.
Ran a Disk Check with both options ticked, to repair - no errors found.

I'm about to try memtest86+ so will see if that shows anything. Other than that, does anyone have any other suggestions?
Many thanks

So I have now run Memtest86+ for at least 7 passes - no errors at all.

Gave up and did a clean install of windows, began installing windows updates etc. Wasn't long before windows froze up on me again.

I'm pretty confused now. If it's a driver problem, can anyway explain how to go about diagnosing a 'bad' driver? There are no errors in device manager.

Other than that, I'm thinking of installing Ubuntu to check if that crashes, or whether it's purely windows related.

The only thing I have tested is the motherboard.

Any help appreciated,
Thanks