I want to set an unbreakable password for windows 7 on my personal computer because my friends mostly guess my password. When they are failed to guess my password they break it with an technique. I want to get rid off this all. I often try to change windows 8 and 10, but they reset all my settings and i loose my privacy. My computer contains my personal data like family pics so i want to them private. My friend break my password and after this they tell me about my personal data that what kind of pic, videos, and documents i have. Me and my friends are room mates. It can be another one who breaks my password for my room mates. My laptop is secured because i have an fingerprint privacy on my laptop but any type of password on windows is easy to breakable for my room mates which not secured for me.
Remember, depending on your jurisdiction, your friends may be breaking the law.
There are a couple of really neat techniques to create near-unguessable passwords.
The first is online tools: just Google "strong password generator". For your needs, 8 characters should suffice. They should be generated randomly. If you can remember a phone number (typically 11 characters in the UK) you can remember 8.
The second is to pick four words at random, and then a capitalisation strategy of your choice. resilientHORSEBATTERYstaple would do.
A third technique is to use an equation. FIVEtimes5=25 or 5*five=TWENTYFIVE! would keep you safe.
However, a Windows password alone won't keep you safe if your friends are able to boot using a Live CD. This may be a bit advanced for you, but consider using an Encrypted Windows install next time you install Windows, or putting a password on your Bios. The Bios password is hard to do, and if you mess up you can break a lot of things, so just go with the above strategies as a first attempt.
Hope that helps!