I have Laptop Dell Inspiron 1545 with service tag 2T0P2K1, when i press the power button the computer asked me for administer or system password and show this massage " This computer system, #2T0P2K1-595b, is protected by a password authentication system, ....) thanks for your help.
try removing CMOS battery,, although I wouldnt know exactly where or how hard it is to get to on a laptop,,
secondly, did you buy this second hand? I wouldn't say that is a service tag,, would probably be an identifier for the PC when it was used in a business location and it would be password protected because of that,, are you getting the password request before a BIOS post? I am thinking it is probably the password request to get into the OS,, in that case you will need to reformat and reinstall windows to get your PC to work,,, you can even test this with an UBUNTU disk, pop it in the tray and you may be lucky enough that PC is setup to boot from disk before HDD and then you can go in and reformat the HDD from there (plus this would prove that was not the BIOS prompt) and then put in the windows disk.