Its a fairly clean XP 64 bit install. No browser add-ins, not even Google Toolbar.

Installed software of possible note:

Skype
Citrix GoToMeeting
Visual Studio 2005 (for developing C# .Net web apps)
SourceGear Vault client (source control with Internet connection to repository)
Outlook 2007

I’m sure that Skype and GoToMeeting were not active when the CPU was locked. However, it is possible either a Skype phone call or a GoToMeeting had been done earlier before the 100% CPU was noticed.