|In general you can't. However there are exceptions depending on what the password is for.|
1. If the password is for your router, you can reset it to default, check the manual.
2. If the password is for the door to the company where you work, perhaps some security staff member may reset it for you.
Mobo: Asus P7P55D LE
OS: Microsoft Windows 7 Professional OEM
CPU: Core i5 750 @ 2.67 GHz
RAM: Corsair Dominator DHX+ DDR3 1600MH 4GB
GPU: Sapphire 4870 D