Remote Management Access Denied

Hi All, hope I'm not repeating any previous posts here and that I'm in the
correct group, but frankly I'm pulling my hair out with this one.

Senario :

Win2K Server running all latest critical updates and service packs.
WAN consisting of mixed win2k and winxp pc's.
Logged in as administrator

Problem.
On all PC's the network administrator has been added to the local
administrators group to give complete access.
Running computer management, connect to another computer.
Works perfectly on all win2k desktops, but fails on part of the win xp
management.

I have had to add a registry key to allow access to the event logs (previous
to that I was getting access denied).
I still cannot go into system information and view the contents. The message
"the connection to pcname.domainname could not be established..."

I can do most other things.
I am a local administrator ?
It is also affecting the remote rollout of Sophos AV - Win2k pc's no
problem, WinXP will not complete the update.AAAARRGGGGHHHHH!
I have changed the local security policy on the xp pc's to set network
access to classic as advised by Microsoft.

The PC's are Dell Optiplex GX260's.
I have upgraded to SP1.
I have applied all fixes.
One strange thing is that I had to create a registry key to allow dfs to
operate as I was getting grp policy errors. Microsofts kb article assumed
that this key was already there.

Could it be an image problem with the xp from Dell ? I seem to remember
reading somewhere about possible image errors on Dell PC's.

Any help would be very, very, very much appreciated.