how to unlock my desktop computer?

I've never told that I don't know how to unlock a computer.

Anyway, it's prety easy to insert an install CD/DVD or a bootable USB device with the desired OS, and install Windows or Linux on any computer, as long as the BIOS is not password protected.
In this later casse, it's very easy to go to the motherboard maker, download the motherboard's documentation as a single PDF file. Use that to reset the BIOS and you are free to go.
I can't tell Con how to reset his BIOS as I don't know the brand and model of the motherboard because he did not provide it.

Electro
November 2013

In my opinion, telling people that one doesn't know from Adam how to unlock computers is a recipe for more computer theft.

T
November 2013

It depend on how it's locked. If it's at the longon screen, then it's not brand dependent. If it's to reset the BIOS password, you need to get the documentation for your motherboard. Get it from the motherboard maker, not from Lenovo. Some BIOS always ask for a password, even if there is none. In this case, just hit the "Enter" key.

Normaly, you need to provide the password associated to the profile you want to use.
If you lost your password, I can't help you here.
Bring your computer to a reputable computer shop with some solid proof of ownership. For a fee, they can do a password reset.

Electro
November 2013