Yet another "activation" issue

I have a client that recently bought a Dell XPS tower with Windows Vista
Ultimate pre-installed by Dell. Vista was already activated and stayed that
way for about a week. Yesterday he noticed that he suddenly had "27 days
left to activate". He tried to activate over the Internet and it wouldn't
work. I tried to help him with the whole phone activation procedure and it
didn't work either.

Figuring it might be the deactivation issue when installing new disk
controller drivers that everyone is having, I reverted back to previous
drivers which also didn't work. He hasn't made any hardware or software
changes to the computer since he got it.

Then I noticed Windows Update was showing a patch that supposedly fixed an
issue where a pre-activated copy of Vista would deactivate. I installed the
patch, but it didn't work either.

I'm at my wits end with this and don't know what else to do, short of
reloading the OS. The client doesn't want to reload since he just spent a
week getting the computer set up the way he wanted. I'm going to try to call
Dell on Monday to see if they have any ideas why this happened.

If anyone has an idea on what to do, please let me know. Also, if you know
how to fix the deactivation issue when updating drivers, let me know too.
Seems like I'm getting more and more clients that are having this happen to
them.