I am occasionally seeing hard lockups on XP: totally unresponsive to keyboard/mouse, screen freezes at time of crash, no SSH/VNC possible. Very intermittent, nothing in the logs. I never see a blue screen on any kind of error message. I would like to know what I can do to go about debugging this, since:

  • I occasionally see similar problems on other machines that I am responsible for. Better and more systematic crash debugging techniques will be very useful.
  • Sometimes happens several times per week - or even day - on my own machine.

This morning I logged in via VNC, logged out again, 20 minutes later physically sat at PC and it crashed around the time of VNC logout.

I tend to suspect video cards in these kind of situations but it's a modern-ish card with modern drivers (one revision back, but this has been happening for 5 revisions or more) and normally would at least see a blue screen I expect.

What would you suspect? Where can I look or what can I set up for more information? Bear in mind that this happens about once every 3 or 4 weeks, so extensive logging or intrusive monitoring isn't really an option.


Memory has been tested with memtest86+.

There are minidumps, but not many and they don't correspond to freezes (they are all 1 year old). Basic analysis gives code THREAD_STUCK_IN_DEVICE_DRIVER_M in ati2cqag.dll. I think these are probably not related.

I tried disabling VNC Mirror driver for several weeks and still get plenty of crashes.

I've now seen it happen "live" quite a few times. I am moving the mouse, browsing etc. and the whole thing freezes.


Having not seen any crashes for weeks, I got pretty much a crash per day for a week. Yesterday I saw it crash as soon as soon after the bootloader, then at the Windows login screen, then on third attempt when syncing iPhone. Again: all the hardware has been replaced since this started.


One common cause of random lockups and restarts is bad memory chips.

Try scanning your RAM with MemTest86. It can be found on many rescue disks, but the one I use is SystemRescueCD.

  • Although the memory was new anyway, I've now done 2.5 full standard passes with memtest8+, no errors. – Sam Brightman Dec 2 '10 at 5:29

A hard drive or other similar on the way out could cause similar lockups then crashes as the drive becomes unresponsive and Windows locks up waiting for the drive to respond. If the drive has an intermittent power fault that causes it to power down briefly then it can cause lockups as from experience I can tell you that Windows does not like hard drives or cd-rom drives (especially the system drive) disappearing while it's using them.

  • Not saying it's impossible, but the hard drive is new and kept cool. Also, in my experience HD failures have other indications - at least blue screen/strange noises etc. I have nothing: no blue screen, no minidump, just total freeze. – Sam Brightman May 15 '10 at 8:48
  • Fair enough, if it's new then it's less likely to be the problem. I just recently had to diagnose a problem quite similar to this and the only symptoms were random reboots with no sign of problems like an error log or blue screen and one particular drive (maybe) taking longer to appear in the BIOS POST screen than it would normally. Took the drive out and no random reboots which is why I thought it worth mentioning. – Mokubai May 16 '10 at 7:58
  • My mistake, I do have one older HD in there (although still relatively new). In fact, I reconfigured it as boot drive and forgot. It also sometimes takes a while to get to my boot loader. Perhaps this is important. Not sure how I will test without replacing... SMART and other HD diagnostics first maybe. – Sam Brightman Dec 2 '10 at 5:37

reseat memory chips, video card, power jacks

check fans

you can download some Live Linux CD (Knoppix, System Rescue etc.).

Boot from there and play a little bit with.

Check temps: CPU/ HDD

check S.M.A.R.T.

open many apps

  • Never happens in Ubuntu. Memory and SMART already tested, temps normal. Now using filtered, surge protected power on top of modern PSU which claims to do the same thing. – Sam Brightman Jan 1 '11 at 17:43

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