Systems Management

I'm implementing Software Update Services 1.0 with SP1.
The client tool name is: Microsoft Windows Update Auto Update Vesrion: 5.4
System Requirements for Windows Update Tool
Automatic Update applies only to the following operating systems:

Windows 2000 Professional with Service Pack (SP) 2
Windows 2000 Server with SP2
Windows 2000 Advanced Server with SP2
Windows XP Professional without SP1
Windows XP Home Edition without SP1

My desktops are Windows XP SP1/win2k professional SP4

Ok windows automatic update tool is included with win2k SP3+/winXP SP1+. The question is why the policy keeps asking to install while the software is there from the beginning. Shouldn't the software deployment which is part of the group policy figure it out without trying to install it each time.
The big question is should I remove the software deployment package from the group policy to resolve this problem. But I'll put it back when new desktops are added and then remove it again? (not a practical solution)

One last thing and it's another point in the big subject SUS. The updates doesn't install on all desktops!! desktops with updates applied through SUS are both XP and win2k. Desktops that doesn't update also from both OS.