Laptop not powering up

[mrapoc]

Got a laptop to fix

Even with mains in, u press power on, fans spin up for 10 seconds, nothing on screen and the power light does not come on, in fact the hdd lights up for like, a second?

Only thing i can think of is open it up, mess with the cmos, check for anything disconnected, cant see it overheating so quick, even then the screen shud come on unless somethin has frazzled

its an old HP, not sure how old but it came with XP and looks retro