Resolved During the sleep mode, it sometimes wakes up automatically for no reason.

The mouse is plugged into the PS/2 port; the keyboard, a USB port.

 

Then maybe you should try a USB mouse.

 

When the mouse wakes the computer, the device shown by 'lastwake' is not the Controller which is the culprit.
So why do you think that the mouse has to do with the unexpected waking up?

 

Don't know. I do know that USB 3.0 failed to fix some problems plaguing USB since 1.0. I also know moving connected devices to USB 2.0 ports sometimes fixes problems.

PS/2 does not use USB.

Heavy footfalls and bumps can cause a mouse to wake a computer (if wiggling the mouse normally does). So we used flip the mouse on its back.

 

Is Windows fully updated? What are you Windows Update settings?

 

Unless you use a PS2 to USB Adapter.

 

Hi Matthew Wai, I have viewed your System Details and with regards to your PSU. You show a 250w unit - your Manual states:
ASUS H81M Series
1-17
•
We recommend that you use an ATX 12V Specification 2.0 compliant power supply unit (PSU) with a minimum of 300W power rating. This PSU type has 24-pin and 4-pin power plugs.
We recommend that you use a PSU with higher power output when configuring a system with more power-consuming devices or when you intend to install additional devices. The system may become unstable or may not boot up if the power is inadequate.

Are your 2GB's RAM just one stick?

Did you follow the recommendation when installing the CPU you chose?
Again from Asus:
Pentium G3240 (3.1GHz, 2C, L3:3M, GT1, 53W, rev.C0)
ALL 0909 GO
*1.Before using the new Intel 4th Gen Core processors, we suggest that you first download the BIOS updater for new Intel 4th Gen Core Processors and then update the BIOS using this tool. 2.Due to iGPU limitation, 4K UHD display is not supported. This relates particularly to the CPU you chose.

Have you plugged your Keyboard into the USB2.0 connector?

Have you moved any of the jumpers on the Motherboard? Neil.

 

I think I have found the culprit and the solution. The culprit was the USB keyboard plugged into a USB port/hub. The solution is plugging it into a PS/2 port using an adapter. Just so simple. Thank all of you!

 

Simple maybe, but not sure it makes sense.

You already said the mouse is plugged into a PS/2 port. Is that really a USB mouse with a PS/2 adapter too?

If this is really a PS/2 mouse and PS/2 keyboard, it may be time to buy new of both.

 

It is a PS/2 mouse without an adapter.

I like the mouse; I won't replace it. It is a USB keyboard rather than a PS/2 one.

 

Does the following make sense?
When the keyboard was plugged into a USB port/hub and it woke the computer, lastwake showed the device was the Controller, the culprit.
When the keyboard was plugged into a PS/2 port and it woke the computer, lastwake showed the device was this thing which was not the culprit.

 

I violently moved and shook my PS/2 mouse, but my computer still did not wake up. Nevertheless, the mouse is sensitive while being used.

 

I have just updated the BIOS. The user guide says that updating should be done before loading Windows while booting, but I successfully updated it using Windows 7.

 

Believe it or not, two weeks ago my motherboard died after my moving the jumpers. Fortunately it was newly bought, so I could get a new one for free.