2 Domain Admins, 1 Gets Admin Rights, 1 Doesn't

I am set up in the Domain Admin and Administrators groups in my Windows 2000
Server active directory. There is one other person in these groups. We both
have identical setups within AD.

We both used to use Windows 2000, then XP, and both had all the same local
permissions, as expected.

However, we then both upgraded to Vista Business on identical machines, and
the other user gets full access rights (ie writing a file to c:\ or looking
at ALL files in c:\Program Files). I however, get Access Denied when trying
to write a file to c:, and have to go to
C:\Users\DJI\appdata\Local\VirtualStore\Program Files\ to get some of my
Program File data.

We have both done clean installs and still get the same problem.

I am guessing somewhere deep within AD I am not quite the same as the other
user, but I don't know where to look, either in Vista or Server 2000

ANy help would be great

Thanks