Login problem

I received a disk of my website from the person who created it. Before I received it I was able to log in. I uploaded it to microsoft frontpage 2002. I made a change to my website and used ftp to load it on the server. Once I did that I could not log in to wordpress. I than upgraded to 2.3 and I was able get my log in screen and logged in successfully. I than made another change and it went back to not being able to login. What am I doing wrong? Thanks