|You can get the IRQL_NOT_LESS_OR_EQUAL error from many causes, but sometimes it can be just because the ram module contacts are not getting a good connection - this worked for me when I got that error:|
A common thing that can happen with ram, even ram that worked fine previously, is the ram has, or has developed, a poor connection in it's slot(s).
This usually happens a long time after the ram was installed, but it can happen with new ram, or after moving the computer case from one place to another, and I've had even new modules that needed to have their contacts cleaned.
See response 2 in this - try cleaning the contacts on the ram modules, and making sure the modules are properly seated:
For a laptop, you must remove both its main battery and AC adapter before you do that.
If you do a ram test, do that AFTER having tried cleaning the contacts and making sure the ram is seated properly - otherwise any errors found may be FALSE.
If the ram is incompatible with the chipset, it will likely FAIL a ram test - that is NOT a true indication of the ram being faulty - there is probably nothing wrong with it, and it will pass the test if installed in a mboard it is compatible with.
If a ram test DOES find errors, if you have more than one module installed, try the test with one module at a time - sometimes they won't work properly when more than one is installed, but it will pass when by itself.
If you want to try a memory diagnostic utility that takes a lot less time to run a full pass than memtest86 does, this one is pretty good - Microsoft's
Windows Memory Diagnostic:
It can be toggled (press T) to do a standard or a more comprehensive set of tests - use the default 6 test one first - if it passes one pass of that, use the latter one. A few of the tests in the latter set are intentionally slower.
If you don't have a floppy drive, see the Quick Start Information at that Microsoft link for how to make a bootable CD of the Windows Memory Diagnostic (you need Windiag.iso - you don't necessarily need to use the program they mention to add it to the CD).
"Also will Memtest tell me if it's the RAM sticks or the motherboard slots?"
A memory test cannot tell you that - it can only show you whether or not you are experiencing ram errors. I've never encountered a mboard that has a bad ram slot, unless it was damaged by installing a ram module backwards in it and then attempting to boot the computer, in which case the circuits for that ram slot are destroyed and cannot work at all.
Contrary to popular belief, it is extremely rare for ram that worked fine previously to go BAD, and almost impossible for more than one module to go BAD at the same time.
When you test ram and get ram errors, the problem is almost always caused by a poor connection in the ram slots, or because at least one of the ram modules is not 100% compatible with the memory controller built into the main chipset or on more recent mboard not compatible with the memory controller built into the cpu.
This probably does not apply to your case because it appears the ram you last installed worked fine for a long while, but it certainly can apply and is a common problem people can have these days:
Ram that works in another mboard , or any ram you buy or have lying around, may not work properly, or sometimes, not at all - even if it physically fits and is the right overall type (e.g. SDram, DDR, DDR2, etc.; PCxxxx, xxx mhz) for your mboard. In the worst cases of incompatibilty your mboard WILL NOT BOOT all the way with it installed, and the mboard may not even beep - the ram has to be compatible with the mboard's main chipset, or in the case of recent mboards, compatible with the memory controller built into the cpu.
If you still have the ram that was installed when the system worked fine, try installing just that ram.
See response 5 in this for some info about ram compatibilty, and some places where you can find out what will work in your mboard for sure:
Correction to that:
Once you know which module ID strings work in your mboard, you can get them from anywhere you like that has ram with those ID strings.
If you have brand name ram, it is usually easy to look up whether it's ID string is in a list of compatible modules found by using your mboard or brand name system model number.
If the ram is generic, that may be difficult or impossible.