BIOS is the lowest-level operating system on your computer; it's responsible for regulating many computing functions such as the processor speed before your computer even boots up. Resetting the BIOS password can be necessary where you have forgotten or misplaced it. Without your BIOS password, your computer will be unable to load. There are a number of ways to reset the BIOS password, ranging from free to potentially expensive, so begin with the cheapest and work your way up from there.
Navigate to http://www.xs4all.nl/~matrix/mpwlist.html, which contains many master passwords for all types of BIOS. Master passwords are secret "backdoor" passwords that can get you into your BIOS even where it is locked. Navigate to the section of the page for IBM computers and try the passwords listed to see if they unlock your computer and reset the BIOS password.
Telephone IBM technical support or e-mail support through the company's webpage if Step 1 doesn't work. Tech support will likely have the most current master passwords for your model of Thinkpad if the ones listed above do not work.
Telephone a computer repair technician and request a BIOS chip removal or jumper reset if the previous steps don't work. Removing and replacing the BIOS chip on the computer can reset the password, but this should not be attempted by laymen, as laptops are notoriously difficult to disassemble and reassemble properly.