Microsoft last week posted a script you can download and run to install Windows XP Service Pack 3 Release Candidate 2. But if you're handy with the Registry, you don't need the script – instead, you can edit the Registry yourself. Here's how to do it.
I'm still installing SP3, so can't test this out myself at the moment. But I've looked at the Registry, and following is the change I've seen. (By the way, if you don't know your way around the Registry, don't do this. And it's always a good idea to set up a Restore Point before hacking the Registry.)
First, create the following new Registry key:
(Note that it needs to be one single, long key with no spaces.)
Now that you've done that, create this string value for the new key:
Give the that string value this value:
That should do the trick.