This is NOT a quick solution. But here is what you can do.
Contact someone locally who will know your are the real owner or administrator. That person can help you recovery the password with method we do not post here.
A possibility is you local police department. The likely have meet up with this kind of thing before. But if you want to contact the maker of the computer, you need some way to prove ownership. If the computer was registered, and recons kept, that would not be an issue.
In the future, keep records. And install TWO users on the computer and two passwords. If a user is an administrator, he can change passwords.
Aldo, get a
cloud service and use a different password. Sore on it a document o reveal the passwords you used. A set of questions that would provide a hint to the password.
Your middle name?
Four digits of your SS#
Tour favorite vegetable?
Or whatever might help you recall.
The cloud server can be read from another computer if you remember the password. In some cases even the cloud server might let your change the password via e-mail or a text message.
That is the best I can do without bending forum rules.
Good and Free cloud servers:
Microsoft
Amazon
Google
Salesforce
..and many others.