Windows 7: Random black screen, rig stays on !!

I've had this before but can't remember what I did to stop it
It Is exactly like you pull the dvi/hdmi lead out of monitor/gpu everything still working i.e. if playing video on youtube it carries on playing just no picture.
I think it was something to do with Intel's built in gpu, but I have disabled it everywhere I can think of bios, device manager etc.
Can anyone through some light on this please as it's startingto annoy me now

My rig specs in sig.

When does this occur? At random? Only when videos/games are playing? Also, what is the exact behavior? Is the monitor giving off behavior as if it has lost its video source, like an error saying the source was lost or it is switching through different connections to find one? Can you tell if your system is locked up, or if it's still accepting your input? The best way to determine thsi is to have the display lost when playing a video, then pressing a key to stop/start playback.

If the monitor is acting like it's not connected to the PC, then it can be a bad video port on your card, a bad/loose video cable, or the monitor itself has a bad port or is just plain bad. You will want to start with potential physical suspects before dabbling with software. Have you tried actually running the video through your onboard video (make sure to enable it and stuff of course) instead of your graphics card and see if that worked?

It Occurs at random, doesn't matter what i'm doing on the net, gaming or nothing even. I get a no signal input message but I can still input to the computer itself, tried both ports on card and changed cables changed monitors changed gpu's still doing it.
Sometimes it will do it once or 3 twice in a few minutes, sometimes it only does it every few hours.
I am almost sure that it had to do with intel onboard gpu.

Changed monitors as well? This is quite odd. How long did things work out for you after you fixed it last time?

Have you updated BIOS/chipset drivers? Also you may wanna fiddle power options, especially LSPM (Link State Power Management) under PCI Express in the advanced power settings (which you can find by going into your current system's power plan).

Honestly, this sounds like a messed up motherboard. You wanna make sure that no caps are bloated or popped on it, and also make sure everything's clean, especially your PCI-E slot.

It's been fine for a while but I have just finished re-doing my water loop, so I could have conceivably distrubed something, just updated the bios rom today to see if made any difference which it didn't.
I will have a look at LSPM in the bios just make sure I didn't miss anything, I have my power plan set to never off atm as well. Bit weird it is cos it hasn't done it since this morning when it did it twice in about 20 minutes.

I reckon you take a gander at the internals of your system and ensure everything's properly seated and cables are connected nice n flush.

Btw, when you connected different monitors to it to test out, are these all the same model of monitor? Perhaps there's some funky sleep thing going on with em?

I will over the weekend thanks for the input, 2 heads better than one. Or in my case half a brain cell cos I can't remember what caused it last time.

No I tried 2 others one old Dell 17" and my spare one Asus 22" also tried different connectors d-sub, dvi and hdmi.

One thing I didn't see in this conversation: RAM. Definitely make sure everything is seated properly inside; but also check for faulty RAM. It's far more likely that a GPU or memory will go bad than it is a CPU issue. I recently had a custom build with this issue (full functionality minus video) brought into our shop. The last thing I checked was the processor; and lo n' behold, it was an ivy bridge chipset on an Asus board, but the CPU was an intel core 2 extreme... It wasn't even a 1366 socket... Regardless, check your memory, it's the cheapest thing to swap.

Ok will do it over weekend.