Frequent lockout of administrator

Hi experts,

I am facing a problem of frequent lockout of the Administrator user of my NW2004S preview installation. The install is a 90days eval copy and still 42 days are remaining. I am aware of the procedure of unlocking using SAP* but it takes a lot of time and I would like to know what and where is going wrong and rectify it.Any pointers?

Rgds,

Amol