XP Service Pack and the end of the happy days...

Here goes....

Have a customer who has been harping on about wanting a SUS server to ship out all the updates to XP machines as soon as they become available. I've put him off for ages because I've had a 50% success rate with SP2, one of the failures was my own laptop, which had no spyware/etc anything on it, as it never gets connected to the internet. I had to rebuild it.... anyways I digress.

Have a site with 21 Dell PC's, they are identical, from the same batch and built with the same image, all users have admin access to local PC for one of the applications that they run.

SUS installed and the initial 7 PC's were placed in the policy to allow the updates from the server, I used option 4 Download and install. Out of 7 PC's only one installed the SP2 silently, all the rest have had various issues. 2 asked the user if it was ok to install the service pack, and said it would after 4 minutes if no response was received, 3 had the icon pop up in the system tray saying new updates ready to install, and had to be installed manually. The remaining PC didn't pick up an update until I restarted the Updates service, then I had to choose the option to install from the icon in the system tray.

The PC's that now have the service pack 2 on are taking between 2.5 minutes to 4 minutes to logon, even after several reboots, previous login time was less than 40 seconds.

So first question.... Why the different behaviour on the PC's?
Aside from uninstalling SP2, how can I improve the login speed?

Somedays I'd rather be fishing for smelly old boots in the canal..... :sad:

All PC's have Norton Corporate Edition installed, windows firewall has been disabled, DHCP running on network, latest drivers on all PC's from Dell website. Initial boot up to login screen is normal.