How do I access a second hand personal computer without microsoft username and password?

If the PC is signed in with someone else’s Microsoft account and the password is not available, the practical path is to create a new local administrator account on the PC, then use that account and remove the old one later if needed.

1. Back up any important files first. Removing an old account can delete data stored in that profile.
2. In Windows, open Settings > Accounts > Other user.
3. Under Add other user, select Add account.
4. Select I don't have this person's sign-in information.
5. Select Add a user without a Microsoft account.
6. Enter a new username and password to create a local account.
7. After the account is created, go back to Settings > Accounts > Other user, select the new account, then Change account type and set it to Administrator.
8. Sign out of the current account and sign in with the new local administrator account.

If the goal is to use a Microsoft account afterward, the local account can be switched later:

1. Open Settings > Accounts > Your info.
2. Select Sign in with a Microsoft account instead.
3. Follow the prompts.

If a brand-new Microsoft account is needed, create one first by selecting Create an account or going to https://signup.live.com, then complete the email, password, name, region, birthdate, captcha, and verification steps.

If account creation fails, supported alternatives are:

• use a different sign-up method, such as email instead of phone number
• use a different device
• set up the PC with a local account first, then switch to a Microsoft account later

Important:

• An old email address from a previously closed Microsoft account cannot be reused for a new Microsoft account.
• Deleting the previous Windows account removes data stored in that user profile.

References:

• Manage User Accounts in Windows
• Change From a Local Account to a Microsoft Account in Windows
• How to check if your email address is a Microsoft account
• How to create a new Microsoft account
• How to change the Microsoft Account owner for my Windows PC without Microsoft account access - Microsoft Q&A