TriggerFinger

Power management chip? Hmmm may be it's integrated and could mean replacement of the whole mobo.

If overheating continues, it could be the fan not running up to speed. Since you have another T22 or a T23, try swapping the fans.

I am assuming you still cannot enter into BIOS setting (or if you can, you cannot stay long) because your LCD screen or external monitor blacks out after some time. If this is so, this is not good as this could mean a video chip malfunction. This could also mean a bad motherboard since the video chip is integrated.

May be you noticed I always emphasize 'entering the BIOS' and nothing beyond that. I do this because at this point, it does not involve Windows or normal HDD activity yet. You can say we are just working at it on purely hardware alone.