Having recently had previous problems resolved via DAL support I now find my computer crashing (screen goes black, no buttons or mouse works, I cannot open task manager etc.) when I either play a game, watch a movie or just now when watching a news video, any ideas ???

Well, sadly, you told of nothing of your computer.

This could be heat problems, power problems, driver problems, or hardware problems - which means it may be difficult to troubleshoot.

If the screen goes black, how do you know Task Manager is not opening? How do you get out of this situation?

Is the interior clean of heat trapping dust? Have you scanned for malware?

My PC has been cleaned up via help from yourself and Broni and I have regularly been checking for malware since and all is clear.
PC is Packard Bell, ixtreme M5722, Intel core 2 quad cpu Q8300 @ 2.5ghz 2.5ghz, 6g Ram 64bit os, running windows 7 home premium
Basically nothing happens when the pc crashes I have to switch off nd back on again then restart windows normally.
I will have a look at the dust issue and let you know

When looking for dust - inspect the motherboard for bulging or leaking electrolytic capacitors. These failed or failing capacitors are a common cause of sudden, but seemingly random system lock ups and reboots. The capacitors look like tall soda cans, many of which surround the CPU socket.

Do you know what your temps are?

Just had a look around, hardly any dust, had a clean of what was there, could not see anything obvious as you describe on the mother board, unfortunately I have no idea re Temps, is it easy to find these

unfortunately I have no idea re Temps, is it easy to find these

I have a canned text for that:

I would keep an eye on your temperatures, particularly, the CPU temps. Your motherboard utilities disk should have a monitoring program (or check for a more recent version on your motherboard or PC maker's website). If none, I recommend CoreTemp for newer Intel and AMD64 CPUs, or RealTemp for Intels. SpeedFan is a great and popular alternative, or you can try Motherboard Monitor. Unfortunately, I have found that these programs often have problems properly identifying and labeling the sensor they are reading. The temperatures shown are as accurate as the inexpensive, low-tech sensors will allow, but it may say System Fan instead of CPU Fan. Fortunately, the programs do allow you to edit the labels, so I use Everest to verify the temperatures (as it is able to match sensor with label correctly), then edit the label in the monitoring program. In Everest, look under Computer > Sensor, then wait a couple seconds for the readings to appear. Unfortunately, Everest does not minimize to the system tray to show real-time temperatures, otherwise, you could use Everest instead of the others. Check but do not rely on the temps shown in the BIOS Setup Menu. While they are likely correct, running the BIOS Setup Menu is probably the least demanding task you can ask of your computer so it does not show the temps when the system is being taxed. But if the BIOS Setup Menu temps are high, you have problem that needs to be corrected. HWMonitor, from the makers of CPUID is also very informative, but does not minimize to the system tray.

Hi Digerati, Temperatures as indicated on the attachment

Those look good. If me, I would want to verify I have good power by swapping in a known good PSU or having your's tested. Everest from above will report your voltages and if good, that is a good sign, but not conclusive the PSU is stable and the power is clean.

Thanks digerati, I have downloaded everest but am not sure what to do with it now I've seen it running, what am I looking for and what should I be doing

Hmmm, well. I am afraid I might have led you astray. I thought for sure voltages were listed in Everest, but I don't see them.

But now, after running Everest myself, I don't see any voltages there either. And when I ran Speccy and SIW on my systems, they both said my +12V is around +6V and I know that is not right because my system is running fine. So, right now, I am at a bit of a loss, except to say that swapping in a known good supply is a better test.