I've generally found that with OS service packs, it is better to get the version aimed at system administrators rather than the chopped down auto versions or the early releases. They can cause no end of trouble.
Two examples: Using the automated MS system to update XP to SP2 went via Internet Explorer, so of course it would have to shut down IE in order to update it as part of the service pack, which meant you could lose the connection because it was also using IE for the connection to the update, so then the update would screw up, then you couldn't instigate it again, because of course you were halfway through updating - result - a hung system that needed a complete format of the drive to sort out. That doesn't happen with the admin versions, because they are the full thing and can be installed whilst offline.
Another example: I made the mistake of installing a beta of IE 7 once, and it was okay, it worked, but thereafter, it would not uninstall and would not autoupdate either, again forcing a wipe of the drive to get rid of the thing.
If you system aint broke, don't try to fix it.
Chock