Someone posted a problem on this thread a while back that sort of went unanswered for a while...well at least went without a *good* answer.
I thought I'd post my answer to this blog as well for people trying to use the XPSViewer to protect XPS files using the Passport service, that don't have Office.
You need a mechanism to get a RAC (Rights Account Certificate (also called a GIC (Group Identity Certificate)), and a CLC (Client Licensor Certificate) from the Passport service. First make sure you have the RMS client installed for your platform. You can get it from here (look at the right hand side of the page).
Then download this file (I provide no warranty for these files. Use at your own risk):
http://www.joectzn.com/ActivationTools.zip (These are just two samples from the RMS SDK that have been compiled)
*Yes, joectzn.com is going to be my dumping ground for samples and stuff since I can't upload stuff to these servers.*
Unzip them then go to a command prompt (CD to the directory you unzipped the tools to) and type:
ActivateGic -U email@example.com -P
Obviously firstname.lastname@example.org should be whatever e-mail account you are signing up for, or have already signed up for the passport service.
Follow the steps presented. This will go out to the Passport services and get you a GIC file which is needed to participate in the whole Passport/RMS world (assuming you don't already have an Enterprise RMS server).
This should go grab your CLC which is essentially your offline publishing certificate.
You should see all of these certificates located in your %userprofile%\AppData\Local\Microsoft\DRM folder on Vista, or %userprofile%\Local Settings\Application Data\Microsoft\DRM on XP and below.
Once you have all of these certificates, you should be able to RMS/Passport protect XPS documents with just the free viewer and the free Passport service, and don't need to have Office Pro+ installed, making the Office team very sad indeed. Now of course if you want to protect things like Word documents, Powerpoint documents, or e-mail you will need Office 2003 Pro or Office 2007 Pro+, but for those of you who just need to protect XPS docs, this should work...errr...at least on Vista x64 where I just tested it. I *assume* it will do the same thing on other platforms.