weird error on installing postgresql in Windows XP

Hi,

I have installed previous version of postgresql. 8.x. I uninstalled it.
Then remove the superuser in My Computer ( right click ) --> Properties
--> in tab Advanced --> Settings button. I try to install postgresql
8.0.1. In service configuration, I checked the install as service
checkbox. Filled the form. After suggesting me to change the weak
password, it said that Internal account lookup failure: No mapping
between account names and security IDs was done.

What is going on here????

Thank you.....