Forgot your Mac or Windows password
There's usually a way back in through your Apple or Microsoft account. The thing to protect is your files, so go carefully.
What's usually going on
Most computers today are encrypted, which is good for security and means there's no back door. The way in is the account the computer is linked to, or a recovery key created when it was set up. Wiping the computer always works, but it also erases everything on it.
Worth trying first
Try the password hints first.
Check Caps Lock and the keyboard language. A password that has worked for years and suddenly doesn't is often a stuck key or a different keyboard layout.
Mac: use your Apple Account.
After a few wrong tries, the Mac offers to reset the password with your Apple Account. Follow it. You may be asked for your FileVault recovery key if you saved one.
Windows: reset your Microsoft account.
If you sign in with an email address, choose "I forgot my password" on the sign-in screen, or reset it from another device at account.live.com/password/reset.
Find the recovery key before going further.
On Windows, BitLocker keys are often saved at aka.ms/myrecoverykey under your Microsoft account. On a Mac, the FileVault key may be on paper or in iCloud.
Avoid password-removal tools.
Programs that promise to bypass the password can damage the system or the files, and some are malware.
When to hand it over
If the computer uses a local account with no recovery options, you can't find the recovery key, or the files on it aren't backed up. We'll find the safest route in. Sometimes the only way forward is to erase the computer; we'll tell you before anything is lost.
Your own technologist, on call.
Tell us a little about your setup. We'll take it from there.