Password nullification

I have a computer (Tower) which hasn’t been used in a few years; but now I would like to use it as storage for my files. The problem is that the computer was part of a network which was password protected, the network no longer exists. The computer is a Dell tower running Windows XP. How do I get rid of the password to get into the computer without re-installing the OS? I would like to keep all the software, applications, data and OS intact. Thanks.