2 years ago i made a password on his lenovo netbook?

Where is the password? BIOS? OS? What is your OS?
Any tech question it is always a good idea to provide as much relevant information as possible. Imagine if you were fixing it, all the questions you would have to ask yourself.

If it is the BIOS password, you can either get into the BIOS (F2 or F10 key repeatedly (not both together - try F2, then F10) before the OS starts booting.) Just getting into BIOS doesn't mean you will be able to change it;usually require old password to change or delete.
Another option is to remove power to the BIOS usually in the form of a battery/supercap. Have a look on the net or in the handbook you may have received when you bought it. Look for BIOS power reset or something similar. The newer laptops, netbooks etc use power from the main battery/adaptor to charge a supercap. These usually discharge completely after 30 days.

Assuming you run a WIN OS later than XP:

If it is your OS you have forgotten the PW for, things should be a little easier. You are going to need another PC with CD burning and internet access. Google 'ophcrach' and download the LiveCD version.
Use this to burn your CD. I'm assuming you have a DVD drive on your netbook-not likely… If not look on the ophcrack website about loading the Live software on a USB stick - it won't be hard.
When you have your ophcrack loaded and ready to go it is a simple matter to follow instructions and reset/clear your password.