I've only noticed this happening in the last week or so and the only thing I've done since then was move house. The only difference was that I used my phone as a modem for the first time ever - a lot of googling for the last few days has led me here but so far there are dozens of theories and no confirmed solutions. In my case, this is quite random. The process called 'System' (description NT Kernel and System) randomly seems to max out one core of the CPU then stops after a random amount of time. There's nothing in the event log for when this occurs. I've run all the malware, AV, etc scans. Almost everyone with this problem that has reformatted and done a clean install says that the problem persists which indicates either hardware or a root kit. I've run 14 hours of memtest which came back clean and I've disabled my wireless card. Nothing has helped. One thing that is interesting which I have found in all my research is that it may be related to IRQ settings. The reason I say this is that one time it occurred was while playing a game and the sound from my Creative SB X-FI went into a very short loop (about 50-100ms). There has also been a lot of talk about Interrupts, USB devices and hardware conflicts which all point at an IRQ problem. I have previously had my hardware working perfectly and then my sound card suddenly stop working for no reason and playing musical chairs with PCI cards changed the IRQ settings and fixed the problem. None of that explains the random nature of the current issue or why there has been a sudden increase in this problem recently. My hardware is a Phenom II 965 with 4GB RAM, ATI 4850, X-FI Fatal1ty and TP-Link wireless-N card (can't remember the model number and I'm at work right now).
