Yesterday I did a PSU test with OCCT and the +12V was way too low. The readings were between 8.58V and 8.64V. My system hasn't been overclocked or expanded since we bought it, except installing a new GPU, the GeForce GT520. Not a heavy one, since it uses no auxiliay power connectors.
It's also rather strange that apart from that my system wasn't unstable. No crashes, shutdowns or anything that's not supposed to happen.
These are my specs:
Mobo: ASUS P5N7A-VM
CPU: Core 2 Duo E7400 @2.8 GHz
RAM: 2x2GB Corsair
GPU: Point Of View GeForce GT 520
Storage: 1x1000GB SAMSUNG HDD
Optical drive: HL-DT-ST DVDRAM GH20NS15
Please give me some good advice, because I want to replace my GT 520 with a GTX 650Ti.
What PSU are you using? Since you only describe it as "400W", I'm guessing its a generic supply.
You'l want to replace that, this one seems to have degraded a fair bit if its giving 8.6v not even under load.