I am running Windows 2000 on a Pentium III 733 with 128 MB RAM. For the last two months on random occasions, the machine will suddenly blue screen and put up the following 4 line message. First line: ‘STOP 0×00000000a 0×00000002′. Second line: ‘IRQL NOT LESS OR EQUAL’ or ‘XMODE EXCEPTION NOT HANDLED’. Third line: ‘Dumping physical memory to disk’. Fourth line: ‘Beginning dump of physical memory’. The last line is followed by a count down from 1 to 99 after which the machine restarts itself and all appears normal until the problem returns. I have not observed any pattern to this problem which happens when using a range of products. Hope you can explain what’s causing this problem and how it can be cured.

We will first concentrate on the IRQL NOT LESS OR EQUAL form of the message. This type of STOP message occurs when a kernel process attempts to access a segment of memory at a Interrupt Request Level (IRQL) that is too high. Kernel processes can only access other processes which have a IRQL which is equal or lower to themselves (as suggested by the error message). The kernel is the central core, much like a nucleus, of an operating system which provides services for the rest of the operating system. There are several possible causes of this error. Firstly, there could be a ‘buggy device driver, system service, or BIOS’ (as Microsoft TechNet describes). This error would occur after the buggy component (eg. driver) has been installed. If you installed a new device driver, application or hardware (eg. if you upgraded your computer) just before the problem first occurred, then try uninstalling/removing the component to see if the problem persists. Should that work, then try obtaining an updated driver or software patch, or if the problem seems to be hardware related, you may need to see your hardware vendor to swap the faulty hardware item for one which is fault free. However, you mentioned in your question that this problem occurred only randomly in the past two months. If the problem doesn’t repeat itself semi-regularly, then it may be difficult to diagnose the faulty component by the process of elimination because you may remove a good component believed to be buggy only to find that the problem occurs in a month’s time. However, a way to identify the problem device or driver is to look at the System Log in Windows. Go to the ‘Start’ menu > ‘Settings’ > ‘Control Panel’ and open the ‘Administrative Tools’ control panel. Open the ‘Event Viewer’ and then click ‘System Log’ in the left-hand pane. This logs all major system events for most of the past year! Try and find the last time you experienced the error (you can put all the events into chronological order by pressing the ‘Date’ column heading). Once you have found the event, double-click on the record. In the window that appears, there should be information on the device causing the error. From there, you can decide on the corrective action, such as updating the device drivers or replacing the device altogether (for example if the problem is a buggy video card or RAM stick). Another good idea is to download the latest Windows 2000 Service Pack in order to fix any bugs.

With regard to the second type of message, XMODE EXCEPTION NOT HANDLED, I have not been able to find any references to this message. The closest I have found is KMODE EXCEPTION NOT HANDLED. However, the KMODE message is probably very similar to the XMODE message you are experiencing. This message means that the kernel has tried to execute a disallowed processor instruction. One reason this might occur is hardware that is not compatible with Windows 2000. Check that any new hardware installed before the error appeared is Windows 2000 compatible. Secondly, as mentioned previously, a buggy driver or system service can cause the problem. In addition to this, conflicts between devices can also cause the problem. You can check for conflicts by going to the ‘Control Panel’ and opening the ‘System’ control panel. In the window that appears, click the ‘Hardware’ tab and the ‘Device Manager’ button. In the next window that appears, look for any devices with an exclamation mark icon which indicates a problem. If there are any, double click on the device to reveal the problem. There are many other possible causes of both the IRQL NOT LESS OR EQUAL and the KMODE EXCEPTION NOT HANDLED errors. Although I can not list them all here, the above mentioned are the most probable. For a full list of all of the causes, have a look at the Microsoft TechNet page www.microsoft.com/technet/prodtechnol/windows2000pro/reskit/part7/proch33.asp. Be aware that quite a few of the points are highly technical and I strongly suggest that you do not fiddle with anything that you do not understand. If you would like clarification on any points, then please feel free to contact me again.