There can be two types of error arising from virtual memory:
1. A STOP error stating “DRIVER_IRQL_NOT_LESS_OR_EQUAL”
2. System low on virtual memory
Cause: Let’s take the first case. Virtual memory is the swap space used by Windows that creates an illusion of larger system memory. This space is allocated by the OS under the primary partition (in most cases). NT calculates this space as RAM + 12 MB, whereas Windows 2000 and Windows XP counts it as 1.5 times the amount of RAM. A STOP error occurs when the area on your hard disk that contains pagefile.sys (the virtual memory) gets corrupted. When the real system memory is low and the page file thus allotted is also low, applications that use RAM extensively issue a ‘System low on virtual memory’ error as the requirement shoots over the total memory (RAM + virtual memory) available to the operating system.
Solution/Workaround: To rectify the first problem, all you have to do is relocate the virtual memory to another partition. Let’s assume the system has 256 MB of RAM; the virtual memory should ideally be 1.5 times the RAM, that is, 384 MB. But this value may be insufficient if Windows XP is installed running many memory-hungry applications. So, take three times the size of RAM if the system RAM is less than or equal to 256 MB. The safe value in our example would be 768 MB.
To administer these changes, go to Control Panel > System. Find “Virtual Memory” and click on it to change the settings.
For Windows XP users, virtual memory is located under the ‘Advanced’ tab of the System Properties dialog box that pops up on double-clicking ‘System’ in the Control Panel. Click on the ‘Change’ button to change the size of the virtual memory. Choose an initial size and final size for the page file. You can also choose to change the partition under which the page file should reside. Set the values and apply the changes. You will have to reboot the machine to effect the changes.