I bought a Dell Latitude D620 Laptop on EBAY.  It came with XP installed and some software where I was able to  log in before the Windows page.  When Microsoft decided not to support XP anymore, I up graded to Windows 7.   Microsoft decided to upgrade me to Windows 10, without my permission.  Windows 10 corrupted my C drive.  Now I want to go Back To Windows 7.  I do not have XP disks and I have exhausted all of resouces.  Can anybody help me?