Cerebr_, thanks again for your very useful replies.
...And excuse my ignorance, but I thought if I did a format of it while it's still in the PS3, it would go back to factory settings.
E.G, be exactly like it was when I first turned it on.
I thought it would do a more selective format, not just wipe everything!
It is originally a 3.55 model (CECH-2502A). So i'll need to find a "OFW 3.55 PUP file", right? Like you said, i'll have a look for the tutorial on these boards. Hopefully all goes well despite my computer-stupids.