Possible causes are faulty hardware, ie memory, motherboard, hard drive; software, including the Operating System itself, with missing or corrupted system files; malware, ie viruses, Trojans etc.
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The simplest way of Windows 7 Memory test is by control panel and it can be done in these methods. Click the windows start option and open the control panel and select the system and maintenance icon in the control panel. After selecting system and maintenance icon pick the administrative tools and click the memory diagnostics tool option in the system administrative tool. The final stage of the process is to restart the system and you can find the errors occurring while rebooting your computer. While running the memory diagnostic test after reboot or you can reschedule it to next reboot. If your system shows any error while your computer boots it will scan and show at next booting of your system. We can also stop the process of memory test in between by pressing ESC button in the keyboard.
Also run check disk on the hard drive.