This is a computer that is almost "dead",its previous owner sold it to me at a low price because he forgot his login password ,and it hasn't worked for 4 years ,i don't know if i still have a chance to make it work.
Because it's a difficult task to log in again (Without password) .
So i need some help ,thanks.
Well they aren't going to give you his old password.
He forgot the password ,maybe that's why it's so cheap .
Why not set a new password for your computer , but this can only be done after the old password has been reset .
Share some tutorials with you so that you can get some tricks to reset password on Windows computer:
https://www.recoverywindowspassword.com/bypass-windows-10-8-7-login-password.html
https://www.lifewire.com/ophcrack-livecd-review-2626148
Why not set a new password for your computer , but this can only be done after the old password has been reset .
Share some tutorials with you so that you can get some tricks to reset password on Windows computer:
https://www.mobiledic.com/windows-topic/bypass-windows-password.html
In my opinion ,as how to reset the old password ,that is what OP cares about.
The password could be reset using Microsoft Diagnostics and Recovery Toolset (DaRT):
https://docs.microsoft.com/en-us/microsoft-desktop-optimization-pack/dart-v10/
https://www.top-password.com/knowledge/forgot-windows-admin-password-try-dart-locksmith.html
or use third-party freewares including Offline NT Password & Registry Editor:
https://www.lifewire.com/free-windows-password-recovery-tools-2626179
But I would recommend you format the drive and do a clean reinstallation to gain the best performance.
The password could be reset using Microsoft Diagnostics and Recovery Toolset (DaRT):
https://docs.microsoft.com/en-us/microsoft-desktop-optimization-pack/dart-v10/
https://www.windows10passwordreset.com/
or use third-party freewares including Offline NT Password & Registry Editor:
https://www.lifewire.com/free-windows-password-recovery-tools-2626179
But I would recommend you format the drive and do a clean reinstallation to gain the best performance.
The Microsoft does support some methods to do that,but i not sure that helps everyone.
Anyway,you can try it for your computer,as well as these methods can be tried.
I don't know whether the OP is still wrestling with this problem...He hasn't logged in in a while...
As others have stated/implied, the optimal fix for finding or bypassing the login password depends on the version of Windows. A fresh Windows install might also be possible, if the Windows product key is known or can be found (whether it's on a sticker or stored in the BIOS, etc.). Of course, before doing anything, I'd make a Clonezilla image of the drive in case I'd need to go back to the original state of the drive.
I just wish I knew people who will sell a PC cheaply due to a forgotten password. If nothing else, I could always wipe the drive and install Linux. 
This is a computer that is almost "dead",its previous owner sold it to me at a low price because he forgot his login password ,and it hasn't worked for 4 years ,i don't know if i still have a chance to make it work.
Because it's a difficult task to log in again (Without password) .
So i need some help ,thanks.