I was able to install SPS2003 on my OS2003 box SPS2003 was running on
http://sps2003:8000. My computer name was 'AMMAD'. While I was trying to
explore SPS2003, I got a need to install 'Active Directoy' (AD). I
was/am novice to AD as well. During installation I entered the DSN name
as 'AMMAD' and there was confiliction with this name ( I don't remember
the exact errror message). The installation wizard automatically chose
'AMMAD0' and I continued with the installation.

After accepting all most all default entries, I was finished with
successful installation (I thought that). After restarting machin when I
tried to log on http://sps2003:8000 using my previous admin account
'AMMAD\Administrator' I was getting error
'No mapping between account names and security IDs was done'

I am still able to browse
http://localhost:12453/SPS/Default.aspx (SharePoint Portal Server
Central Administration for AMMAD)