Laptop is asking for password (which I never set), even when without hard-drive
This is the BIOS administrator password which you may set in the BIOS setup option. Without giving correct password , you can't even enter into your booting. If you forget your password, give your laptop to the service center. they will remove your password.
Its the cmos battery, remove the ccmos battery down and login again after that the password will have been removed, you will then set your date and time and after that put in the cmos battery there again...its as good as ice cream