uplugging cmos battery won't help, passwords are stored in EEPROM on modern lenovo laptops
All lenovo laptops have additional master password.
If you have a proof of ownership or registered your warranty with Lenovo, their support will be more than happy to guide you thru the reset procedure.
For obvious reasons, i will not go into further details how to reset it, but be assured it's fairly quick and painless process if you can prove to Lenovo it's really your Laptop.
master password is maybe not an accurent word.. basically bios will generate a specific key, they'll input it to their system and it will return "master password". It not the same for every unit. But Lenovo being one of the big dogs on the block, want a little mulah in return