I have an older Latitude E5520 that has been in sitting for a few years.  I didn't write my windows password down and and I guess I forgot what I thought was the password.

     I want to install a solid state drive in it but have no way of finding the windows enterprise product id so I can reload windows.  

At one time  I would use this one program to get that product id from the registry but if I can't log into windows there is no way for me to find it.   I also thought that I could download the original windows operating system from Dell's website by putting my service tag in but it won't work ?

  Any suggestion on how I can get windows back on this new hard drive.  I only use this one program that won't run on windows 8 or 10 so I need it back working after I install this new hard drive.  Thanks for any help.