Laptop not booting up

[avg123]

My old Toshiba C870 laptop is not booting up. It was giving the CMOS battery low message for a couple of days and I had to set time and date before booting.

 

Today it also showed that message but this time after setting time and date, the laptop does not boot up.

 

I replaced the CMOS battery. Waited 1 hour after taking out old battery and putting in new one.

 

But laptop simply does not boot up. I can go into bios, change boot order but it does not boot up from harddrive or usb.

 

I have checked the hard drive in another hard drive and it is fine, I have checked usb drive with windows 10 installation and it is also fine.

 

I have replaced ram sticks, tried booting up without the DVD drive and hard drive, directly into usb drive but nothing works.

 

I have to mention the laptop battery is completely dead and laptop does not turn on without it being plugged in but this was the case for a long time with no problem.

 

When the laptop turns on, it just show a blank screen, then restarts and show a unblinking cursor at the left top corner of screen for sometime and restarts again and keeps doing this