how can i unlock my laptop ibm thinkpad 600?

That password is contained in the hardware and is designed to ensure that stolen ThinkPads turn into scrap.

You should ask the person that you obtained the ThinkPad from for the password.

If you can't get the password for any reason, if you take it an IBM/Lenovo dealer they may be able to help you but it won't be cheap (Usually a Motherboard replacement) and is really not worth the effort on such an old machine. (Ten years or more.)

If you recently bought this from a dubious source then you have just learned a lesson.

T
November 2009