Now I had a problem running adprep because it was from x64 R2 CD2 and I was trying to run it on Win2000 Server. So what I did was, I got win32 version of R2 CD2 and run adprep on my Win 2000 DC, both /forestprep and /domainprep, and then DCpromo was done with no problem on my new Win2003 R2 x64 server...