Upgrade Ultra ATA cable and Fan CPU

That's likely resin residu from the soldering. I do notice however that the area around the clock capacitor still seems to have some leakage residu. Maybe you couldn't get it more clean? The rest of the pcb looks pretty dusty as well.

 

Possibly is from the electrolyte leaked from the old clock cap. I've seen some leaks that were quite small and others that covered huge areas of the motherboard and made it to the bottom of the case.

 

Hey nonosto check pm