Dont attemp to install windows 98 anywhere unless you know and understand how to first hide Win2K and install a boot manager. I don't know if Win98 would let you install over but if you should succeed you will not be able to boot up the installation even if you can find a way of overcoming the password problem.
If by administrator you mean your name as an administrator that is one thing. There is also an actual account NAMED Administrator, which if a password was never set for will get you in straightaway. In the box where the login name appears just type in Administrator with no password and report back.