For OS5 & W(windows) series NAS:  (For OS7 Intel X86 NAS with HDMI/VGA model, please scroll down)
Please power off NAS eject HDD & SATA DOM, arrange memtest86+ to verify memory compatibility & system stability, with following steps:

A-1. Make MEMTEST86+ driver

Method1: (newer version)
M1-1 Create from Windows 9x/2K/xp/7, download and execute from your PC and would clean USB driver up and install this tool & bootable:
http://www.memtest.org/download/5.01/memtest86+-5.01.usb.installer.zip

Method2: Traditional DOS boot
M2-1: We need prepare an USB driver as a Free DOS bootable disk from:
http://rufus.akeo.ie/ or https://github.com/downloads/pbatard/rufus/rufus_v1.1.7f.exe
M2-2: Copy memtest86+-4.20.exe.zip and unzip the MT420.EXE into USB driver.
http://www.memtest.org/download/4.20/memtest86+-4.20.exe.zip

 
A-3. Plug USB driver into NAS back panel USB2.0 port, and USB keyboard.
A-4. Power up NAS & N2800/N4800/N5550/N7510/N4510U & press F2 into BIOS. (N2810, N4810, N5810 press DEL)
A-5. Config BIOS boot menu booting from USB driver.
A-6. Boot into DOS, type "MT420.EXE" for memory testing at least 24~48 hours.

B. Since enter the MEMTEST86 and system would auto start testing, as like following link picture, the top line have PASS & TEST running, and at middle left the WALLTIME is running, if get error would could found from middle-right the ERRORS & ECC ERRS.

http://www.memtest.org/pics/i875-big.gif

C. If MEMTEST doesn't running automatically, please help us doing compare test from an normal PC/NB to confirm the USB driver & MEMTEST is correct.
C-1. Take this USB driver into a normal PC/NB, boot from USB and doing MEMTEST 86 testing, to confirm this USB driver & MEMTEST 86 is working.
C-2. Remove the additional memory from NAS and doing the MEMTEST again.

For OS7 Intel X86 NAS with HDMI/VGA model:

1. Power NAS OFF.
2. Eject HDDs out with order.
3. Link NAS to monitor with HDMI/VGA & USB keyboard.
4. Press power button make NAS up and wait:
    BIOS post screen disappear or 12~15 second  (ex: N2810, N4810 15 sec & N5810 12sec)
5. Press ESC key.
6. Should have following screen show up and choose Memtest86+.
7. If without menu to choose Memtest86+, please restart from steps 1 and extent longer second until following screen.