Fix Driver Irql Not Less Or Equal Error

May 28th, 2009

Device drivers are required to allow operating systems to communicate with computer hardware. In Windows XP and Vista quite a few device drivers are included with the installation. But for a lot of hardware, special device drivers are required. If drivers are corrupted or not installed properly, Windows will report a device error. One of the device errors that the Windows can report is a “Driver Irql Not Less Or Equal” error. This can result in a blue screen.

The irql less or not equal error basically indicates a problem with the system resources used by a hardware device, such as I/O address ranges, DMA, and IRQ’s. The IRQ is an interrupt request, which is used by the hardware to claim CPU time from the system. The number of IRQ’s in a PC however, is limited so sometimes different devices end up sharing an IRQ.

The Driver Irql Not Less Or Equal error can happen in Windows XP as well as in Windows Vista. The irql error can happen with the NDIS.SYS file, if the error is caused by a network or modem card, but other hardware can also be the cause of the conflict. Because of the severity of the this kernel level problem, the error results in a blue screen or stop error. Driver errors would normally be obvious because the blue screen error lists a .SYS file.

Using the .SYS filename, you can find out which device or hardware is responsible for the error. You can then disable the hardware in the Windows Device Manager to see if the device is really the cause of the error.

Running a memory test is also a good idea, as faulty memory can be the cause for many stop errors. In the Bios, disable the quick start, so the full diagnostics is run, and a memory test can be run using software.

In most cases the ‘irql not less or equal’ error can be solved by updating the drivers for the device causing the error. Also make sure you update your Windows and antivirus software, as some of these errors are not caused by hardware, but software problems. You can use the Windows device manager to uninstall any currently installed driver for the device and the reinstall the latest driver. When you reboot your PC after uninstalling the drivers, Windows will detect the new hardware, which allows you to install the latest drivers for the device.

If you do not have the drivers for the device in error, or are not comfortable in using the Windows device manager, you can also use a driver update program to find, download and update all device drivers for you. Driver update software will accurately identify your hardware, including the device in error, and automatically install the latest drivers for it. This can solve driver irql not less or equal errors.

If updating the drivers does not fix the issue, try loading the default BIOS options. This will ensure that RAM timing, FSB timing, and CPU timing are not causing the error. Further you can check the resource assignments on the devices in the Windows Device Manager to check if there is an irq conflict.

Microsoft further advices that you try to load the last known good configuration using the start menu (press F8 during boot). But you do need to make sure that the problem does not introduce itself again as a result of changes or updates. So the best way is to find the real cause of a blue screen error and fix it.

In case you are still running Windows 2000, there is another possible cause for the driver_irql_not_less_or_equal error, which is related to dismounting drive volumes. Check the Microsoft knowledge base article on this to fix it.

Entry Filed under: Device Errors