Try replace cmos battery with a new cr2032. Then clear cmos settings by motherboard RTCRST jumper which is located here [IMAGE]
Hello everyone, I have an OptiPlex 790 SFF computer and it's been giving me trouble lately. First, when I powered it on, it displayed the unsupported video configuration error. The display was connected to the dedicated graphics card at the time, so I assumed that the graphics card was defective. I removed the card from the system and when I attempted to power it on, the system just didn't power on. It flashed orange on the power button a few times but that's all it did.
Dell OptiPlex 790 not powering on