Defective RAM can cause all sorts of problems. If you're suffering from frequent crashes, freezes, reboots, or Blue Screens of Death, a bad RAM chip could be the cause of your travails. If these annoyances tend to happen when you're using a memory-intensive application or game, bad RAM is a very likely culprit.

But that doesn't mean it's a sure one. You still need to make sure that the problem is with your RAM, and if it is, you need to identify the bad module.

The best diagnostic tool I know for the job is the free, bootable MemTest86. Since it's bootable, you need to put it onto removable media. You can download separate versions for installing the program onto a CD or on a USB flash drive.

The CD version comes as an .iso file. The USB version comes with a program that prepares a flash drive, so that it can boot your PC and automatically run MemTest86. If you're not familiar with booting from an optical disc or a flash drive, see Boot discs explained: An overview of booting your PC from something other than your hard drive

If you go with the USB version, you'll have to launch an .exe program in Windows, which brings up a busy and possibly intimidating little program. Don't worry; just go through the four steps onscreen. And don't use a flash drive with files that you need on it.

Once you've prepared the boot media, shut down your PC. Then unplug it, open it up, and remove all but one RAM module. If you're not sure how, check your manual. You may want to wear an anti-static bracelet for this job.

Then plug in your computer, insert the CD or flash drive (if it's not already inserted), and boot. You may be told to go into Setup because of the RAM change. Do so. Once there, check to make sure that it's showing the right amount of RAM, correct it if it isn't, then  save and exit.

The PC will reboot again, and MemTest86 will start automatically. It will test all of your RAM, and when it's done (which could be an hour or more), it will start all over with a second pass. Just to be safe, I recommend three passes. Or you could start it before going to bed, and let it run all night.

If it finds something wrong, you know you have to replace that RAM module.

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