I am all locked up.

I have a DELL Inspiron 7500, running Windows 2000 Professional. I made a few changes on my domain and network connections and now I cannot log in after I restarted my computer. It is saying invalid user or password. I am getting this after the computer has booted and I am on my username: an password: first prompt. I know the changes I made are causing this problem, because I was trying to eliminate being on a network so I erased the user name when I was making the changes. I am no longer on a network, so I was trying to erase all the information I had installed when I was at my prevoius employer. Is there anyway for me to get in my computer now or do I trash it?
Please Help.
BS