What is wrong with my PC?

Nov 30, 2018
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My PC is 7 years old. Here's my rig:

1. i3-2120
2. Corsair 4gb RAM x1
3. Seagate HDD x3
4. Nvidia Palit GT710
5. Asuz Motherboard
6. New PSU with 700w (Replaced my old 600w)

I don't have case fans. I'm using Windows 10. I know its way too old but throughout the years, this is the first time I encountered this problem. When turning on, it suddenly shutdowns on its own. I checked the BIOS immediately and found out that my motherboard has a bad reading, in voltage category (5v), it reads 6v and indicated RED, which is above normal.

Here are the list that I did so far but still no good.

1. Load defaults in BIOS
2. Cleaned everything with blower
3. Replaced PSU
4. Detached every cables/wires and put it on back
5. Removed all the components and assembled it again
6. Removed HDD then boot
7. Removed Vcard and used the default slot for monitor, then boot
8. Removed RAM then boot

I am open to any suggestions so I can fix my rig. This is the only treasure I have. Please help me. Thank you.