Okay, so you forgot your password for logging in to Windows. All is not lost. You can still log in to Windows—even if there is no other administrative account on the PC.
From a security point of view, this is actually scary news. But there are legitimate reasons to use the tricks below, and none of them will let a criminal log in without your knowledge (the password is changed, not revealed) or gain access to encrypted data. (You do encrypt your sensitive files, right?)
I’ve provided instructions here for Windows 7 and 10. Windows 8 users should have no trouble following the Windows 10 instructions.