XP – Unwanted ISDN call outs.

I have a remote client who decided to install a Win XP PC on their LAN. The LAN segment has an ISDN dial-on-demand link to another site. Since installing the XP PC they have found a substantial (HUGE) increase in the cost and number of ISDN calls made from the site. They have little local expertise.

Before I start a detailed analysis of this problem, I thought I would ask if anyone has any related information. I have already worked on this problem (or very similar sounding) at sites running W2K that were trying to get to blackhole.isi.edu to register the computer name. Does anyone know if the same problem or similar exists under XP?

Thanks