Question My Lenovo IdeaPad G560 turns on, but has black screen, what should I do ?

[RandomUserr]

So, about 6-7 years ago, a Windows update was stopped on my Lenovo IdeaPad G560. At that time, if i turned it on, it gave me a black screen and a mouse. That was all.
About a week before, I was throwing away some old things, and I stumbled upon it, so I thought I will try to fix it. Currently, if I turn it on, about 3-5 seconds later it turns off. If i turn it on for the second time, it does start, but the fans are really loud (I think they are going on max), and I don't get any screen.

I cannot even boot into BIOS. I tried switching HDD, but nothing changed, so it's not the HDD's fault. Another thing: the small led lights work (like the one that lights up if i'm charging the battery), but the lights on the front panel edge (Caps lock) does not. I took out the two ram sticks too, hoping I get somekind of output from the main board (Yo, there's no RAM i give you some high and low pitch sounds), but nothing. I think it's something to do with the processor or/and the main board, what do you guys think?

I did asked this on other forums too, so I will answer some questions I got there:

1. You should boot from a windows setup disk.
I can't, because I don't get any screen from the laptop. I can't even boot into BIOS, because I don't see anything. I tried it on a external monitor and a TV too, and I still got a black screen.

2. CMOS battery is dead.
It can be dead, but I searched about this topic, so what happens if the CMOS battery is dead, and the other websites said you can still boot into BIOS and your notebook will work.