"Unfortunately, access to computers can, at times, be blocked for all of the wrong reasons. Sometimes this occurs due hardware related issues such as electrical problems or due to inadvertence, such as someone setting and then forgetting the password. It can happen as the result of accidental use of a Bios password by a new user. This also often occurs when an employee who is quitting or has been terminated, sets the Bios password as some form of retaliation against an employer. Reversing this can be time consuming as well as very frustrating depending upon the motherboard manufacturer and the make and model of the motherboard. Relax though, as it is possible to reset or disable the password.
Electrical or static related issues:
At times, and without any obvious reason, static discharges as well as other electrical problems can cause the PROM on the motherboard to reset the Bios (CMOS) to its default values and even cause the default Bios password to be set. These are some of the default Bios passwords used with different Bios's, give them a try first.
AMI_SW (case sensitive)