Sorry for my long, long post, but this is a big problem, and it needs solving. I didn't know where else to post this, but it may help other people reading this, if it is solved. I've never had a problem this bad before, with any kind of computer. Who hasn't heard of the many infamous problems where a computer shuts down while booting up or so? Oh yes, but this is different. Now you may be thinking, "different? but how?". Well that's part of the problem, you see. About a week ago, my computer shut down as soon as I plugged in an USB device (incase your wondering, it was the USB cable to transfer pictures etc. to my cellphone). My computer was idle at that point, but nothing more than about 2 seconds had passed when my computer suddenly shut down. I thought "nah, what the hell?" and plugged out the USB cable, and booted it up again. This time it shut down during the boot process (think it was when windows logo was showing, or about at that time). I tried to start it again, foolish as I may be, yet it didn't even power on. I spent no more than about 5 seconds of pressing the power on button, when I noticed a smell of burnt hardware. I thought this was definately the PSU, bought a new and replaced it. But the computer would start with no picture on it. "Damnit", I thought, pondering what the problem could be. Then I noticed a small spot on a motherboard chip that looked burnt. Today I got a new motherboard. I plugged everything in correctly, except for those additional USB ports on my case front that I had plugged the USB cable to back then. It was booting. "Alright! ... Huh?". My computer shut down again, while booting. This time there has been no burning smell or burnt chip as far as I know, but I can't help thinking what the problem may be. No doubt, it is hardware related, it did the same thing trying to boot from a CD. I tested my ram by replacing it with working ram of the same type, which I had in another computer. Same thing happened. I tried to plug in another disk drive (I'm assuming it is empty, but not sure). Anyhow, my screen didn't turn on. Plugged in my old disk drive, and screen turned on again when trying to boot. So what I'm facing is: Is this a cable problem? Loose connection somewhere perhaps? Or is this a processor problem? I doubt that. It could also be a problem with the graphics card, but I really don't know. I'd like some help from you guys, what could cause a shutdown like this? I'm lost. NOTE: I've heard from others that it might be a grounding problem. It's true that my PC wasn't grounded, but when I tried putting in a grounded power cable, that didn't work either. Just managed to get to vista boot screen, powered off. Any ideas what this may be are welcome.